Your purse or wallet is a key to speedily unlocking £100s of savings. So get it out, and open it up. I'm going to show you how to examine all the main items you keep in there, to check they're the right ones and you're correctly tooled up. If not you can likely save £100s or more.

1. Pull out your debit card - do you have a winner? The debit card shows where you bank. Here are my key questions...

- Do you pay a monthly fee? If so work out its annual cost (£15/mth = £180) and then ask yourself if the 'extras' they give are worth this. If not, cancel it. Plus if you were flogged it or told you had to have it, you may be able to reclaim all packaged bank fees.

- Are you overdrawn? Debit cards can be debt cards too. For small overdrafts you can switch to First Direct, which gives you £100 which will help clear it, and a £250 0% overdraft. If it's bigger you can use a 0% card to clear your overdraft.

- Does your bank make you happy?
If not, again First Direct is worth considering. It gives newbies £100 to switch, and has won every bank service poll we've ever done, with 92% of its customers rating it 'great'. Plus you also get access to a 6% regular savings account.

- Do you have savings?
Bank accounts pay the highest interest: Santander 123 pays 3% on up to £20,000; Club Lloyds 4% on £4,000 - £5,000 and TSB 5% on up to £2,000 plus up to £5 a month cashback on contactless purchases.

Switching account these days is quick and easy for most, and can be very lucrative, as Janet emailed: "Been with our old bank for 50 yrs, we were nervous about switching but it all went perfectly, plus we got £100 to spend on holidays. Ta." Full info in Best Bank Accounts.

2. Got an Oyster card? You may be due a share of £200m+. There's big money sloshing about - if you failed to touch your Oyster out you can often claim back the excess (some have got £70 on this). Plus if you now use your contactless card instead, or if you've an old Oyster, you can claim back old credit. See our Oyster card reclaiming guide for how to do all of them.

Martin Lewis
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3. Got a credit card(s) that you pay interest on? STOP. Get a 0% balance transfer, that's where it pays off the debt on old cards for you, so you owe the new card, but at 0%. The difficulty is of course getting accepted, so use our Balance Transfer Eligibility Calc to find which top card you've best chances of getting.

Go for the card with the lowest fee, that you're sure you can pay off within the 0% time.

- Longest no-fee 0%: Halifax* is up to 23mths 0% no-fee.
- Small fee, longer 0%: Barclaycard* is up to 32mths with a 0.72% fee.
- Longest 0%:
If you're unsure, go long: Virgin Money* is 0% for 40mths and the fee is 2.59% (so £25.90 per £1,000 transferred).

Yet never miss repayments and do clear the card before the 0% period ends or they jump to 18.9% rep APR after. Savings can be huge as Victoria tweeted me after using the eligibility calc: "I got my fiancι to transfer his credit card balances to a 0%, saved £1,500 interest." Full help, FAQs & options in Best Balance Transfer Cards.

4. Pull out your driving licence - is it valid? They only last 10 years. A whopping 2.2 million are out of date - check yours or you risk a fine of up to £1,000. Driving licence - what to check & do if it's invalid.

5. Got a credit card and always repay in full? Make it PAY YOU. When you use a card, the retailer has to pay the card firm a transaction fee. With a cashback card you effectively get this put in your pocket. As new regulations have cut these fees recently, cashback's been cut too, yet Amex cards are mostly exempted, so still pay a good whack.

The fee-free Amex Everyday* (eligibility calc) pays 5% cashback (max £100) for the first 3mths, then tiered up to 1.25% after. The best non-Amex is Asda Mastercard* which pays 0.5% cashback (1% in Asda). As Anna tweeted me: "@MartinSLewis Glad I read about Amex cashback card: I'll get over £200 paid".

Yet only do this if you'll set up a direct debit to repay IN FULL each month or you'll pay 22.9%/18.9% rep APR interest, which more than wipes the cashback gain. Full options in Top Cashback Credit Cards.

6. Is it crammed with £100s of coupons? No, why not? You can print 100+ coupons from our coupon page right now, to reduce your weekly shop costs. And to up the gain further, check out Extreme Couponing.

7. Sign up for a myWaitrose card for FREE daily tea and coffee. Then you can get a free hot drink every day from the machine without buying anything. Or if you spend in their cafe, you get a barista-made cappuccino-type drink for free. See free Waitrose coffee for how.

8. Not got a credit card... you're less protected & missing free cash. Credit cards have two roles: 1) a way to borrow; 2) a way to spend. If we neutralise the first by setting up a direct debit to repay IN FULL so there's no interest, and you stick within the credit limit, they become much like a debit card, but with two extra benefits...

- Cashback: You get paid to spend, see point 5 above.
- Extra protection under 'Section 75 law': Buy something costing £100 to £30,000 on a credit card, and pay for any of it (even 1p) on a credit card, and the card firm's jointly liable with the retailer for the ENTIRE amount. This get-out-of-jail-free card is hugely powerful if the retailer goes bust or won't play fair...

As Michelle tweeted us: "Successful Section 75 credit card claim, refunded £125 for non-delivery of phone order, used template on your website, thanks". See our Section 75 - how to use it guide for full help.

PS: If you've been burnt with credit cards in the past, or have little financial discipline, ignore this point; better safe than sorry.

Take Martin's five-minute wallet workout – save £100s
Take Martin's five-minute wallet workout – save £100s

9. Is that a condom in the corner? Good. Safety is important. Worth noting though, all condoms have a use-by date. If yours has gone, you can get them free, whatever your age, from clinics and health services. Find your nearest pick-up point: NHS free condom search.

10. Got a gym membership card - when did you last use it? Nowt wrong if you're a regular, but many pay and don't go, as if somehow just having membership makes you fitter. As Jon tweeted me: "Paid £270 for a year's membership, went for one swim. Most expensive swim ever." So be brutal - cancel if you don't go; there are one-off classes and pay-as-you-go gyms, for occasional use. See Cheap Gyms.

11. Holstering loyalty cards? Max the points. Never choose where you shop on account of a loyalty card, but always have a loyalty card for where you shop regularly. And use them wisely padawans... with a few Jedi tricks you can up the gain. See our points-boosting tricks for Tesco | Nectar | Boots | Morrisons.

12. Breakdown cover card - don't just renew. When it comes to renewal they often just pump up prices. Yet 88% who try to haggle breakdown prices down with the AA and 85% with the RAC succeed.

Alternatively, use AA/RAC cashback sites to get basic cover from as little as £21. Or AutoAid has full service cover (incl home start & onward travel) for you and your spouse (or civil partner) in any car for £42. Peter emailed us: “The AA renewal fee was £199. With AutoAid it cost £42. Many thanks.”

13. Got serious wads of cash? It's not always king. I'm not just talking the risk of having your wallet nicked. Cash is less secure as you don't get Section 75 protection (see point 8) as on credit cards, or even the lesser debit card chargeback protection. If you're going to use cash, always keep receipts in case you want to return items.

I remember being contacted by an old gent (in his 90s) who'd paid a big deposit at a restaurant for a planned birthday bash. The restaurant went bust, he asked what he could do. As he paid cash, the answer was nothing. On debit or credit card, there would've been options.

14. Do you have a donor card? If not, it's worth a thought. It's a big decision, but joining the Organ Donor Register could mean you save or improve up to nine lives. If it's for you, sign up online or call 0300 123 23 23.

15. Do you have a railcard? Families, couples, students, under-26s - if you ever travel by train, get one. Railcards cost up to £30 a year, but get you a third off most train travel. So they pay for themselves if you spend £90 a year, even just on one trip. And there are far more than you think (eg, the Two Together card for any two people). See Is there a railcard for you?

16. Do you have a SAD FART wallet? If not, you need it. SAD FART is my way of remembering your consumer rights, and I've a wallet-sized consumer rights guide you can print out and put in there, so if ever you're in dispute, you're armed. Plus St John Ambulance has a pocket-sized first-aid tips guide too.

17. Do you have an overseas wallet? Savvy travellers have a separate purse or wallet for going overseas. This can seriously save you cash; you can have a look in my overseas wallet here.

This article first appeared in the weekly email on 20 April 2016. Its contents were fact-checked and updated on 26 April 2016.

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