Welding when you’re not 40 anymore…

I am a journeyman welder and did it professionally for over 20 years until my (body) health came into play and I switched occupations.
I still do welding occasionally on my car projects. (usually mig sheet metal repairs/replacement).
Some advise for you guys from me is the most important thing is to understand how it works.
It isn't about ''sticking'' two pieces of metal together, it is about bonding the pieces together properly through a heating and cooling process to make the weld strong.
If you understand what you are looking at while you are welding, you will make adjustments in speed, amperage, angle, and position as you go to achieve the best result, and that takes a lot of practice!
Vision of the weld is crucial (as many have mentioned), and as you get older, it can be a big challenge, but it is key...
The other crucial thing is fit up and cleanliness of the metal and the welding machine and it's parts.
This is VERY important.

Mastering the 6010 rod is quite easy, as long as you realize that it is meant to be a ''cleaning and penetration all position rod'' for rusty or scaled surfaces or bad fit ups.
The 7018 is a finishing all position rod over 6010 or used for clean surfaces with a good fit up.
Most other common rods (6013, 7014) are best used in the flat or horizontal positions.

As for mig welding, I always use a ''push'' technique rather than a ''pull'' technique if fit up is proper for sheet metal.
Good fit up means at or slightly less than the thickness of the wire.
Push technique means that the gun is angled behind the weld toward you and your line of sight of the weld and joint is better, and ''pull'' or ''drag'' is the opposite. Push technique is a lot easier to see too as a bonus, as well as lower penetration for sheet metal.
The bottom line is that when I was in school, we started with an oxy-acetylene cutting torch, then on to gas welding mild steel (brazing) and then on to electrode or stick welding, we spent hours and hours and used up a few hundred pounds of rods to get the technique down pat for it all over several months in all positions.
And I loved every minute of it!

To you people new at it, get the basics and go from there, it is a great idea to get a beginners course under your belt, and it will give you the skills to do basic work on your projects as well as some understanding on how the process works.
Good for you!