"These aren't the answers you're looking for..." - Obi-Wan
First, you should probably read this. I'll answer anyway because it's an interesting topic, but usually the StackExchange sites are about solving issues that you actually face, not "I wan't to learn about cool_thing".
Anyhow, there really isn't a good answer to this question in a practical sense, and it's of dubious legality, but in general you'd want to:
- Use your laptop as a wireless access point. There really isn't any trickery here, people do this all the time (usually as an ad-hoc style network e.g. "Free Public Wi-Fi").
- Hope that the person who's tailgating you has a wireless device that's not currently asleep, off, or dead; and that is configured to autoconnect to anything it sees, or you could use something commonly know as "KARMA" to spoof being his home network.
- Use an exploit to do evil things. Exploits come and go and generally aren't legal but if you're interested for purely academic reasons then there are tons of places to hear about these types of things. I like to listen to "Security Now!". If you want to actually hack stuff, that's not a hole I'm willing to dig into but Google exists. (Keyword: Metasploit)