Hi there I have added answers below for you.

If you were going to travel to Spain to play golf where would you get help to choose where to go? Costa Del Sol has the nickname Costa del Golf there are around 120 golf courses there.

Would you use a website and if so which one or ones? Online Golfer has reviews of some courses down there.
Would you go to your local travel agent? Golf Service are local down here and have some fantastic deals for booking.
Would you go on a friend's recommendation? It is some of the best golf in Europe if they agree yes.
Would you ask on a forum like this? Of course people are the best advert.

I'm asking cos I was asked the question by somebody who has an apartment in Spain and wants to attract golfers.

I simply searched using Google but are there any sites that people would recommend or have used etc.? Might be worth an email to someone like Golf Service to see if they would be able to help them out.

Hope this helps?