Seek out sites whose content complements yours. Link and benefit from a larger community to draw traffic from. Offer extra benefits if you like, but do so in an attitude of giving, rather than getting. Goodwill is paramount. A sincere, personal word of thanks is always appreciated.
Beneficial partnerships deserve to be nurtured.
Seek out available banners or buttons on websites you wish to link to. Follow their suggestions for linking. If you're at a loss for ways to describe your intended links, contact the webmaster and request mutually beneficial assistance. Offer low bandwidth buttons or banners for those who wish to link to you. Visit each of your links on a regular schedule.