Subdomains?? what can I do ??

[wish71]

Hi there...

I'm wondering how can I optimize my website in order to gain a better place in search engine using Sub domains?

I mean www.photo.wish71.net (example) how can be useful in order to optimize wish71.net ???

My idea was to use the sub domains in order to insert in the domains my key words
I mean my website url regretfully has not the keywords that I like ... so maybe someting like ..... keyword.domain.net ..... example if I need photo as keyword.... this kind of subdomain like this will nelp ???? photo.wish71.net

I have not thought to insert link from sub domain to my main domain in order to increase ingoing number of links .... I think will not work at all, will be considered internal link.