Beyond going to the tips in the User Guide, just share lots of legit content so good hosts will try to connect to you, download at peak times (watch the net size, and keep a clean connection to the gnutella net by opening the firewall and mapping your router (if any).

Download speed is determined by the slowest link between you and the file you want. All you can do is have the fastest internet you can afford and tweak the bottlenecks on your system.