Budget flight fee-fighting

Two of our top pick flight comparison sites, Kayak* and Momondo*, let you compare flights including luggage fees. So, if you know you'll need to check bags in, they'll estimate the cost of luggage in the results.

It's a useful feature – other big comparison sites like Skyscanner don't include it. The data comes from airlines, distribution systems and other sources. However it is an estimate – you'll need to double-check the costs before you book.

If you've specific dates in mind, are going further afield or there's no budget airline sale, check for the cheapest flights via comparison websites. Our top picks are Kayak* and Momondo*. But remember to always check a few sites and compare the prices against going direct.

For far more tips – for example, Orlando packages can be cheaper than flight-only trips – see full Cheap Flights guide. If you're looking to fly with Easyjet, see Easyjet Tricks to cut costs with the UK's biggest airline, and see Ryanair Tips for how to avoid sky-high charges with the Irish carrier.

Don't forget to check package holidays either. In traditional tourist spots, for seven or 14 days in particular, package holidays can win, especially if you haggle. Plus you get extra protection if things go wrong. See our full step-by-step system in Cheap Package Holidays.

As you go through the booking process, airlines can try to tempt you to book everything from travel insurance to fast-track boarding.

Accidentally clicking these boxes can be costly, so scroll slowly and watch the total price of your booking doesn't leap up.

They've got sneaky ways of making you pay even if you've got kids flying with you – it can cost a family of four up to £240 to ensure they're together on return flights.

In fact, research from UK regulator the Civil Aviation Authority found British passengers waste up to £175 million a year on unnecessary seat fees. To help, we've airline-by-airline free seating tricks in our Airline Seating guide.

Budget flights can touch down in airports some distance from the city centre, which mean you'll have to pay to transfer to your real destination. 'London' Southend Airport is 40 miles from central London, Stockholm-Skavsta is 60 miles away from the Swedish capital and Oslo-Torp is 70 miles from the centre of Oslo.

So factor in the cost of getting to and from the airport. Take the time of day into account too – if the flight gets in at midnight, a taxi's cost could wipe out any savings if you can't take public transport.

Typos, mistakes and wrong dates can cost large on budget airlines, so treble-check everything before submitting.

Ryanair charges £115 per return to change the named passenger (£160 at the airport). However, it can be sympathetic to innocent errors, for example, if you booked a Ryanair flight under the name Matt, rather than Matthew, as shown on your passport.

You do have a 48-hour grace period to correct minor errors free – if you enter an incorrect nickname, typo or old maiden name for example.

However, if you want to change a passenger's name, say, from Ariel Hassle to Justin Credible, it charges the full fee. Ryanair's press office says this fee's to stop travel agents buying up the lowest-priced seats and reselling them.

If you're doing a budget flight with young kids in tow, check how much equipment you're allowed to check in, as allowances vary.

• Ryanair. You can take one pushchair per child for free, plus either a car seat, booster seat or travel cot. Additional pieces of child equipment can be taken at a cost of £15 each, per flight (£20 if paid for at the airport).
  
  
• Easyjet. For every child, you can bring a combination of two of any of the above items for free.

Child seats are compulsory in Europe for under-3s. Yet from £5/day, hiring child seats from car rental firms is expensive. Some airports, such as Malaga, have places where you can rent car seats at half the cost. See Cheap Car Hire for more.

It's also worth considering whether to take your own seat – for more info, see ex-MSE Steve N's blog on Flying with your own child car seat.