Tip 1 - where to put your main subject
By all means take photos where your main subject is in the center of the shot - it's the sort of picture you're expected to take on holiday. But, once you're taken it, try something a little different. A better photo is to position the subject either in the left or right third and get a nice composition with the background. Photos like this are more pleasing to the eye and immediately make your pictures look more professional.
Tip 2 - keep your finger on the button
Digital photos cost virtually nothing so remember the motto - keep it with you and use it often! Get into the habit of carrying your camera ready for action and never take just one shot, always take a selection to give you the chance to choose the better one of the bunch. You can only take holiday photos once so make the most of it!
Tip 3 - don't be afraid to be different
Never refrain from taking a photo because the conditions aren't quite right or because you don't think it will make a good shot. Many great pictures happen when you have a camera in your hand and luck is on your side! This is especially true on holiday so try it! Take the photo! Take something the 'book' says you can't photograph - if you don't experiment you'll never learn and you just never know what might happen.
Tip 4 - local life
Take a photo of the locals at work and play but always ask permission first. And, if you don't speak the language, waggle your camera at them and smile - if they smile back you're in luck, if not and they look unfriendly, smile anyway and walk on by to try your luck elsewhere.
Tip 5 - know how to use your flash
Flash gives you a wonderful advantage for some photos but learn how to turn it off for taking those photos where you don't need it. In particular, don't take scenic views with flash on because, if it's dark where the camera is positioned, you'll get a bright foreground and a dark view. Learn, too, about other ways to use your flash, for example as a fill in.
Tip 6 - when to take photographs
Get up early and go to bed late - but not on the same day! In the morning the light is better, there are not so many people around and certain things happen that never happen during the day. At night places look different and there is a whole new atmosphere to explore but be wary taking photographs in a strange town late at night - stay safe!
Tip 7 - have fun
Try to enjoy photography for it's own sake and always take some photos just for yourself or as an experiment or just to see how they turn out or because it seemed like a good idea at the time. If you're enthusiastic and having fun with your photography that will spill over and make your shots all the better.
Of course, take holiday photos to show other people but remember that the enjoyment is often when you will look back years later at that holiday so make sure you get a full set of good photos to remember it by.