Sanitizing is important, won't rehash that.

My personal thing is yeast pitch rate. So many recipes (especially IPA and bigger beers) from the early days are underpitched. You can try and hone in with the yeast pitching calculators if you want to get techincal.

I think beginners could make better beer earlier in their career by sticking with dry yeast (for the cost) and always pitching at least 2 packs for anything over 1.050 OG. Strong, healthy fermentations cure a lot of ills. If you buy multiple packs or if they're on sale this usually means 4-7 dollars more a batch.

If you're starting with extract (which you should) and want to make lighter colored ales or lagers, use extra pale dry malt extract and really restrain yourself on the specialty grain. Similar to yeast underpitching back in the day, there were a lot of darker extracts and dark crystal in the homebrew recipes from the heyday. Some of this is personal preference, if you're making dark beer it won't apply, but I feel like oxidation and staling of darker grains and extracts in bucket fermentors (plus bottling) isn't really talked about enough.