The most important thing for a vanilla superhuman run is to understand how to avoid all of the glitches and also to use good battlescape tactics. Beyond that it's actually pretty easy when you take advantage of the abundant resources you have at your disposal:
1.) Soldiers are abundant. It is good to keep them alive and getting experienced, and losing soldiers hurts morale, but a few losses here and there don't really hurt you financially. Don't waste money on armor if it isn't going to pay itself off.
2.) Money is abundant if you keep it flowing in. Go on missions where your expected monetary income is greater than your likely losses. Go on lots of easy missions, especially landed UFOs. Sell all those plasma weapons and UFO Power Sources you collect.
Another tip to make failure less likely: get a hyperwave decoder as soon as possible. Getting a lot of income early on will pay off if you spend it on seeding the world with bases that have a hyperwave decoder, a hangar, and a firestorm with at least 1 plasma beam. Once you're there, the entire game is downhill. Shoot down EVERY infiltration craft, shoot down all retaliation craft except for battleships, and pretty much ignore everything else. Take on landed missions for supplies; if you see an alien base or infiltration mission in final stages, that's a good place to catch several large landed craft.
Another tip: watch your score. Don't run out to kill all alien bases as soon as possible, rather save some for a bad month. You can do a couple of base missions to jack your score up at the end of the month as needed. Also don't be afraid to abuse the warning mechanism. If every other month you get an awful score, you're fine. It's only two in a row that kills you off.
By this point, the game is easy. You can mass-produce blaster bombs with all the elerium you get from missions you demolish by blastering half of the aliens and all their leadership on the first turn. Just make sure you NEVER misfire into your own craft. Then psi-control everything into submission. And have a backup craft/crew because no matter how good you are, you never know when a blaster bomb will end your whole crew. Using these strategies and generally good battlescape tactics, you can have a 99%+ success rate on superhuman ironman.
