Hey, a good place to start would be to find out what self defence/ "martial arts" classes are available in your area. If you want self defence, find a class that allows some degree of pressure i.e. the drills are done with opponants that are resisting (trying to stop you applying your techniques easily). You don't want a class where "attacker" throws one single slow punch and stands there while you apply techniques. Obviously to learn a technique you have to start like this but over time resisting partners are a must!
If these classes aren't available to you then you could try a full combat sport like boxing/ muay thai/kickboxing. You can combine the skills you've learned there with some of the streetfighsecrets dvds/cds. Remember any CD/DVD you buy should be to support your physical training and not replace it.
Do you have a punch bag at home? Do you have access to gymn or weights? Do these alongside any class you find or while you're finding a class that suits your needs. By the way if a class is advertised as RBSD (Reality Based Self Defence) then this (should) be a step in the right direction.
Good luck!