Just use jailbreakme.com or redsn0w. Either should work fine, jailbreakme being the easier of the two. Blackra1n only worked for 3.1.2 and spirit wont work with itunes 9.2 installed.
yeah you use jailbreakme.com i bought a second hand 1g yesterday and i upgraded it from 2.1.2 to 3.1.3 and i then used jailbreakme.com to jailbreak it as blackra1n didnt work and also redsn0w wasnt recognizing the 1g 3.1.3 ipsw file kept saying unable to process firmware so just use jailbreakeme.com it does take quite a few minutes to jailbreak unlike on the iphone or maybe newer toucheswer it is faster but this method is working perfectly fine