This is advice directed if you just want to match... not match at Harvard or John Hopkins. I been on 3 interviews thus far this is what I gathered:
PD don't give a $hit what 4th year classes you take. All they care about are:
a) Board scores? (probably 70% of your ap)
b) Grades? (And really no particular class, just trends. Do you honor? Do you fail classes? And maybe your anesthesia elective grade)
c) Are you personable enough to work with? (IV can either improve or show deficiencies in character. I'm from the school of thought that IVs are just to make sure you're not a nutball or geek.).
d) Class rank, specifically are you at the bottom or high end. Again impress or deficiencies, otherwise neutral.
e) LOR - Ones that are specific to you, and speak highly of you regardless of attendings fame. A famous anesthesiologist who writes 3 sentences about you = worthless. 1 should be from your dept chair of anesthesia, 1 from anesthesia attending, and 2 other ones your choice but the trend is usually 1 medicine and 1 surgery. Just make sure they know you, and take time on your LOR. Most programs only need 3 LORs.
e) Research... depends on the school, some like, some could care less. Either way makes for good IV questions if you did it.
f) Extracircs: Volunteer, prior jobs, ect. is for the most part meaningless. Chances are they didn;t even look at that. Just make sure you have something there. Having nothing might draw red flags.
Now to be a good anesthesiologist (which really won't help your app, but def. prepare you):
1) Pain management - Did an elective and it was awesome. Plus you can discuss anesthesia with the residents because most of the guys did a residency in it.
2) ICU: SICU probably your best bet but they will work you. MICU is good too but not as hands on. CCU no experience in.
3) As many anesthesia electives as possible, of course only at programs your considering going to. Them knowing you beforehand is quite possibly the single best assest to match.
4) Neurology... You will get better at a neuro PE. Assessing reflexs, sensations, motor tone/bulk/strength. Not that asnesthesiologist use it that often but its good to know how to do especially when a block or epidural go horribly wrong.
5) ENT.. You'll understand the throat anatomy better especially when you do scopes and layngeal procedures.
Hope that helps. PS take your step 2 early and rock it if your step 1 isn't 220+... Its becoming more important each year.