As with all other traffic programs involving mass mailing or displaying ads, there's absolutely no effectiveness in selling something straight away unless 1) you can target a very specific market, and 2) there is a cause for urgency.
You will always do better giving out freebies in exchange of the recipients' e-mail addresses through a lead-capture page. What you must continually practice is to create a funnel system like this:
traffic programs -> lead capture -> autoresponder list
so that you are able to qualify interested people into loyal subscribers and buyers. Why? It is always better to mail several times to the same folks who are willing to give you a more positive response than to randomly mail what most others wouldn't care.
Think of a game plan of what you can best do to create such a funnel system.