It is probably already clear from the replies above, but Tor does NOT defend you from revealing your own identity. It doesn't provide end-to-end encryption on regular servers, the last tor relay (the exit node) sees your traffic comming in and out, except it can't link it to your IP address.
There is a nice guide here on the forums that may help you (viewtopic.php?f=4&t=21285
), but I believe anonymity requires you to be careful. I think the Tor browser bundle is probably a very good bet for internet browsing, but in any case, I think it may be a little to easy for you to accidentally reveal your identity if you don't know how Tor works, how HTTP works or what you are doing. This is coming from a programmer's perspective though. You could always believe in Tor and have faith.
I personally wonder though how much good transparently routing all your traffic through Tor would do. If you have applications installed that could communicate with a server (if you're aware of it or not), that don't encrypt their communication and include some information about your system, ip or personal information, that 'might' link you with it.
Keep in mind that the internet is not a trust-less network. Servers get hacked, emails get sold, and then there is the NSA. Also, if you are going to buy weed online, at least one person needs to know your address, and even if you encrypt that, you have to put trust the fact that he won't be sloppy and accidentally leaks the information. Not that I have any experience though, weed is more or less legal here...
Ok, hope this all didn't sound overly paranoid, but hope it helps.