Dennis,
Congrats on taking some welding classes. It is best to learn from folks that have "been there, done that". When you are under the hood, think like a machine. Try a dry run pulling or pushing the gun/stick/ what ever you are using to see if you are comfortable for the run you want to make.... If not, change body posture, bracing etc until you are. You will see how much better you weld once you are comfortable!! Keeping a constant stick out 1/2 to 3/4 with your mig will give you the best results... Also some wires need to be pulled, others pushed. Listen to your instructors....
As for the auto darkening hoods. Find the fastest one you can afford. What I mean by fast is how fast it goes dark. For the weekend warrior that time may not be too important. If you are burning copious amounts of wire or making a lot of starts, the effect on your eyes is cumulative for your welding session. If you eyes feel fatigued, try another hood!!
One more thing. Enjoy yourself!! Try not to weld stuff beyond your skill.. I read on this forum folks giving well meaning advice. However welding is a science..Not difficult, but it is a skill. I have been in the business for over 35 years and I never stop learning....
Please, Never weld brush hog/mowerblades once broken!!! It can be done. However with an approved procedure and some fancy post weld heat treating.
Keep us posted on your progress and good luck!!
Dave.