1. If you don't have a suitcase included in your flight price and don't want to pay for it, hand luggage can be taken and each person is entitled to 1 polythene bag containing their liquids in their hang luggage. Each item of “liquid” can be no more than 100ml and the mag must not be over filled but make use of what you can take
2. Many high street shops now sell packs with empty 100ml plastic toiletries bottles that you can fill with your regular shampoo, conditioner, shower gel etc and take in your hand luggage (see above). You don't need to pay for a suitcase in order to take full size toiletries – especially if it's only a short break when you won't use much anyway.
3. If you're flying on a scheduled airline, many also now don't include luggage unless you're flying on a transatlantic flight (such as KLM, Air France, and all US domestic airlines). Some of these airlines have Frequent Flyer schemes and you can sometimes sign up to the scheme and get a card and benefit from reduced cost luggage or completely free! It's more usual for an airline to offer free luggage with these schemes if you've flown with them before so it can be worth having some loyalty to your favourite airline and definitely worth researching before you travel.
4. Hand luggage can be a small suitcase as long as it fits within the airline's specified dimensions (always published on the airline's website) so if you're travelling for a short break or up to a week, you may very well be able to travel with just a small suitcase and take it onboard, avoiding any suitcase charges.
5. Pack clothes to mix and match and pack travel wash! Packing clothes that can be worn in different combinations and similar, neutral colours, will maximise space in your suitcase as you will need to pack less, meaning you can just take hand luggage. Packing a small (remember maximum 100ml) travel wash will also mean you can do a spot of laundry during your travels and re-use outfits!