Most flight companies will give you at least 20 kilos of luggage allowance and a further 5 kilos to carry on board. Charter flights may give you only 15 kilos and, in the days of the War on Terror (ho, ho) there’s no telling what restrictions airlines will introduce to ensure safety.
Generally speaking, if you’re a few kilos over and the flight isn’t full to bursting point they may let it slide. It kind of depends on your luck with the person at the check-in counter so it’s worth being as friendly and polite as possible. These harassed clerks get a lot of grief from unreasonable passengers all the time and a little courtesy can go a long way.
If they inform you that you’re over your baggage allowance and have to pay extra you can always get creative with your packaging. One trick is to put on all your clothes at once – 4 trousers, 7 shirts etc – and then just get changed again once you’re on board. There’s no rule to stop you doing this if you’re bold enough to pull it off. Heavy objects like books can then be carried in the pockets of the second or third jacket you’re wearing.
Alternatively, good results have been reported by some travelers by collapsing on their knees and sobbing loudly until they’re made an exception of.
Or you can try your luck with hand luggage instead. Often at the check in counter they won’t clock exactly what you’re carrying on board and you can cover your bags up with a coat. Or, if you’re traveling with someone else you can check in separately and get them to wait with your carry-on bags whilst you get your boarding pass. The chances of anyone stopping you at the departure gate are small, though it can happen.
Most of the time you can get away with taking a guitar on board the plane but sometimes they’ll give you grief at the check-in. At the worst they’ll put it in the fragile holder (Oi, Bert, catch! Wot’s this say, fragile? Ho! Ho!) and if it’s an expensive instrument you might want to think about a hard case for it.
Basically, you don’t want to look like you’re smuggling drugs. So a clean, smart appearance is a good start, as are bags packed in a tidy fashion. Either that or leave smelly underwear at the top so they lose enthusiasm fast.
Be very polite to customs officers as they have more power than just about any official in the country. They can detain you, put you in a cell for a day or two without a phone call – all just to see what comes out in your shit.
If you’re bringing in valuable stuff and you don’t want to pay tax then you could always get a false receipt for the items so that it looks like they’re worth less.