to cloak/hide your affiliate link, the best to use is php. a simple redirect is good for very basic need. with php, you can do more then just redirect, you can code a little bit more to capture the visitors ip, time of the click, etc. you can hire a programmer from site like elance & rentacoder to do the coding job.

javascript is not a good choice since more people are disabling the script especially firefox users using the noscript plugin.

html refresh meta is simple but you need to create htm file for each affiliate link, it's nto easy to manage if you are running many affiliate links on several websites.

my 2 cents.