As for heat, I'm using a Miller 180 (a 220 unit) and had it turned up to I think D on an A through E settings. I also had the wire feed rather slow.
I also have the
Millermatic 180 (mine doesnt have an A-E). Follow the power/feed guide printed on the inside of the cover (that covers the roll) - those numbers are pretty much dead on. You can also go to the Miller website, print out the page with all the settings for different material thickness, and stick a few copies around the garage (or the Explorer).
I should also mention that I find it easier to weld when the settings are set for one thickness level below when using 0.30 or 0.35 wire (if welding 1/8", I set it for 14 gauge) - this is not the case however for .024/.025 wire. Anyways, setting for one thickness lower gives you time to deal with the puddle and make changes if necessary.
Looking back at your photo, it looks like you've got that brown powder coming up - thats some form of an oxide. Try to get closer to your weld (minimize "stick out"), change your position, change the welder setting (feed so you minimize heat and CO2 breakdown), or increase the shielding gas flow rate a little (this will cool down the weld faster and also minimize CO2 break down).
Just keep practicing, it'll become almost 2nd nature sooner or later. I first got my Miller at the start of my project and I wish I could go back and redo some of my welds now that I'm finally getting to know the welder a little better.
EDIT -- and for anyone wearing glasses, get some contacts! They make a world of a difference when welding. That and replace the front protective lense of your helmet every now and then (its like $4 maybe).
EDIT #2 -- I found my Excel spreadsheet with the settings. If you have the MM-180, then this should work:
http://izwack.com/dump/weld_speeds.xls. There are multiple copies on the same page cauz I cut them into strips and stuck them around the garage and the Explorer.