I'd suggest using a Contact us page like the one I use for our site (see user profile) that outlines who to contact for what, where and which modes are available, et al.
Ah, the most puzzling of all the holy grails in website marketing approaches and goals. Better you should ask..
"Why would two almost identically profiled 32 year old males buy a battery for their car from different stores? One from Sears, the other from the local auto parts store?
In sales,, as opposed to marketing, the 2nd most important of all is to create urgency; Do something now, contact us. Don't wait... Do it now.
Creating the sense of urgency in the prospective customer's mind requires that you have answered all their initial questions, made the buyer feel comfortable with your goods or services (in that yours are what they've been looking for, after all) and that to look further is counterproductive.
1) Some intense market testing. Have some of your associates browse your site, and pay close attention to their comments.
2) Mirror what your most successful competitors do, as re: look and feel of the site. Why re-invent the wheel?
3) Monitor your log files closely, or invest in Deep Metrix Live Stats (the live tracking is worth it's weight in gold) or WebTrends. Watch paths visitors take through your site, and where they leave from. If they leave without buying or contacting, their exit point would be be your starting point.