1) Be careful that you don't set yourself unreasonable targets. You wouldn't try to see every bird in Britain in a week, so don't attempt it abroad. It's meant to be a birding holiday, not a driving holiday, so base yourself somewhere good, and don't stray more than a hundred miles in any direction. Spend most of your time birding. Who cares if you miss a few species, you can always go back next year. Possibly consider two different bases if you're going for two weeks.
2) Find yourself a "local patch" close to where you are staying, and visit it a few times during the holiday. Just like in the UK, some species need a bit of work. You can't expect to walk straight up to everything.
3) Buy as many decent field guides, maps and site guides as you can find / afford before you go and study them in detail so that you know exactly where you want to go and what you might see when you get there. This can save you hours of wasted time trying to find places on the day.
4) Don't assume that you've "done" a place just because you've seen one or two star species. There's probably plenty more still to see. For example, I have friends who think they have "done" the Coto Donana in Spain, just because they spent one day there and saw Crested Coot, Spanish Imperial Eagle and a few other specialities. We're talking about a place the size of a medium sized English county. I've been there several times at different times of year, and still wouldn't claim to have "done it" (in two days time I'll be there again :t: )
5) If your going to a hot country, don't bother lugging the scope around between 10am and 6pm. It will nearly kill you and be next to useless. Travel light.
This thread should have been started on the Tips for new birders forum.