Offensive Demoman:

1. General Tips
1) Learn to pipejump.
2) Learn to use mirvs. They are very powerful against multiple enemy defense.

2. AutoDet Bind
A lot of the time you may have a defensive demo on your team also. And guess what, he is getting mad because you are stealing his pipes. That is why you should use the autodet bind (See Below). The bind automatically dets the pipe soon after launch, so you wont have a lot of pipes existing at the same time.

FIRE PIPEBOMB AND AUTODET BIND
Command: ( impulse 7;+attack;wait;-attack;wait;detpipe )
Description: This bind will fire a pipebomb without having to switch weapon. It will also automatically detonate it after launched.

3. How pipebombs work when shared
Your team may have a max of 7 pipes. However, if a demo has a trap laid of 7 pipes, and you use a pipe, one of his pipes detonate. BUT, they only detonate if the pipe you launch hit the ground.

4. Learn Pipe Jumping
This is an essential skill. Check out section 1.6, the section on pipe jumping.