Great choice on the saw
it's always nice for us to know somebody is paying attention.
Saw paraphernalia;
Always have a spare chain.
If your a one saw outfit a spare bar is always nice, if you pinch a saw you can take the bar off and put the other one on and cut the pinched bar out.
and having the other bar in a different size is nice for those times when you need more bar. A 24" would be nice in your case.
Get a bar cover and use it.
A spare spark plug is a good idea.
I found out the hard way carry a spare flipper cap
(gas/oil cap) in the truck.
Keep that torx wrench that came with your saw in the truck as well, never know when you might need it and it will take the whole saw apart if necessary.
As was said spare bar nuts.
Spare rim and e-clip.
A spare clutch bearing is a good idea as well.
Wedges - at least two felling wedges and a small 4-5 inch bucking wedge.
Your gonna need a single bit ax
(yes even with a chainsaw), mostly for pounding wedges, but useful for a lot of things in general.
PPE - Chaps
(or saw pants), forestry helmet, gloves, and steel toe boots. Here’s a link if your thinking you don't need it
http://www.arboristsite.com/showpost.php?p=852617&postcount=33
Files for sharpening your chain, my advise is get a "chain maintenance kit".
(Stihl has a nice one)
A cant hook is real nice, not necessary but it sure makes life a whole lot easier.
Of course your gonna need a fuel can, mix oil, and bar oil. The whole fuel/oil thing has been beat to death around here and I won't kick it again (do a search if your interested) I'll just say
IMO use a good high octane fuel and the best mix and bar oil you can find.
Check out some of the online safety manuals, and read the manual that came with your saw.
http://www.tiltonequipment.com/ChainSawOperatorsSafetyManual.pdf
A few links to get you started.
Check out this video on how to sharpen a chain. Just scroll to the bottom of the page when it opens on Ammiks web site.
http://www.amickssuperstore.com/Vallorbe_5_32_Chain_Sharpening_Kit_p/vallorbe%20532%20sharpening%20kit.htm
A real good video, Kinda long but worth the wait
Dial-up
http://www.tilton.usa.jonsered.com/Files/Jonsered/cs/downloads/videos/Working_with_chainsaws_176x132.wmv
High speed
http://www.tilton.usa.jonsered.com/Files/Jonsered/cs/downloads/videos/Working_with_chainsaws_320x240.wmv
Use the search function here and ask as many questions as you need, a lot of great folks around here who are more than willing to help.
Good luck and cut safe.