Top Tip 1:Love this thread, this is one of the reasons I log on here almost every day. There is so much to learn.
Get used to one gun.
Go to lee lightings website for a guide to using filters to balance light.
Your flash is daylight, you might not always be shooting in daylight. Rosco do colour correction packs. Worth the effort.
Top Tip 3:
Forget about the synch speed. Get a flash that supports HSS and put it to the back of your mind, screws things up.
Top Tip 4:
I like to set my ambient exposure for -1 and my flash for -1/3. Won't work for every scenario but a starting point. RAW is your friend.
Top Tip 5:
The rules of on camera flash still apply, bounce, swivel, diffuser etc still all work. A basic stand and brolly kit (reflecter and diffuser, you get mini ones for off camera flash) can make things look grrrrreat.
Paul, I see you have updated your signature with the Powershot now, hope you like it and that it lives up to your expectations.