How do I optimimize my websites to several keywords?

[Macbeth]

For exmaple say i have a website on holidays, i may also want to other keywords which can mean the same thing as travel, tours abroad, vacation etc

How do i do this, and what are the most effective methods?

Are there any implications for SERPS in diffrent search engines, i.e. if you do it one way in Yahoo it could cost you rankings in Google?

[BeeDeeDubbleU]

Optimise different pages for different keywords. Re optimising for the different search engines, they all use different algorithms so their results will be different. It is possible to rank well on all of them - if you are lucky.