You need to setup a squeeze page or have some sort of optin form on a website. Drive traffic to it and offer something free that people will want in exchange for giving you their email address. There's tons of information about it on these boards and posted on articles all over the internet. Just do a little searching.
It only counts as spamming if you don't have people optin. Sites like aweber and getresponse require double optin and make you follow the can-spam act. Bulk emailing does not count as spamming unless you are not following the rules. If you just harvest emails and send out unsolicited emails in bulk then yes it will be considered spam.
spamming will only occur if you use a dodgy server or something like php's mail function if you avoid spammy words like "FREE" (upper case) in the subject you should get past filters fine
email marketing is a risky business if you dont have your own optin list or dont abide by the rule. read the CAN-SPAM rule before pursuing email marketing otherwise you might be in trouble
I have a list of 30 million emails, 26 of them are verified, 1500 are already Used by me .. If you want we can may be get a deal about them !