We brought an apartment in Bodrum (loads of problems with the developer and UK agent, but thats not why I'm here).

If you're buying as an investment the main thing is make sure you can get rental income from it and that it remains a popular development for resale.

Some general advice would be to look at some of the UK private rental websites and see how many properties are rented out for say July/August - high season. Look at what areas/developmetn are booked out, what facilities the sites have, how many beds, what furnishing, what prices etc.
some sites:
Holiday villas, holiday homes, holiday rentals, Private Vacation Homes by owner
Self catering holiday villas, apartments, cottages, for rental worldwide

Good Luck