you could probably start by looking at some of the seo forums on the web for some advice, seochat.com is a good one
In the interim I would begin by adding them to some Directorys with high PR 4-5 and above, and for a start if the sites are the ones in your SIG, change the setup of them so that the Anchor text ( text viewable in your signature ) is a keyword you want to optimize for. Do not simply have the domain name as the display name and then the same for the actual link. I did this and noticed some changes within MSN search in a few days however google will take alot longer, if it will even make a difference at all on its own ,I doubt it.
Also add your sites into the directorys this way so that the main name of the site is a keyword or group of keywords for your site, not simply the domain name.
link exchanges are another one, post in the trade section for a Front Page or link page exchange with other ppl in the same boat ( everybody wants traffic ), sitepoint.com has a section for this in their forums with a greater selection of sites other than webmaster and saturated market sites.
There is obviously alot more to it, these are a few simple ideas. Like I said , search the specific SEO forums for advice and optimize your pages. Do not buy traffic from anybody, do it the hard way and your traffic will be more consistent in the long term!!!