How do I prevent weeds from coming back after pulling them?

The main thing is to pull them out completely - roots and all - since most weeds will regrow from even tiny root fragments left in the soil. After that, mulching the area thickly or using a weed barrier cloth stops new seeds from germinating, which really cuts down on repeat growth.

Don't skip the digging part even if you think you got the whole plant - I learned that the hard way with some stubborn dandelions in my yard that kept popping back up until I realized I was leaving bits of root behind. Once you've actually removed everything, what really works is laying down cardboard or newspaper before you mulch, because that extra barrier stops seeds from getting down into the soil and new weeds from finding their way up. Even thick mulch alone lets some determined stuff through, so that combo of pull-deep, then cover-then-mulch is what finally gave me a season where I wasn't constantly pulling new ones.

Here's the thing though - even perfect pulling doesn't guarantee they won't return, because some weed seeds can lie dormant in your soil for years waiting for the right conditions. Beyond the root removal everyone mentions, timing matters a lot; pull them right before they set seed and you'll notice way fewer recruits popping up next season compared to letting them mature.

Avoid just lopping off the tops and calling it done - that's basically fertilizing them to come back stronger. The ones already mentioned about roots and timing are spot on, but what most people miss is that even a perfectly cleared patch will fill in fast if you leave bare soil exposed. Right after pulling, get something down there immediately: cardboard, newspaper, wood chips, whatever you have. The idea isn't just to block light (though that helps), it's to physically prevent new seeds from settling in while you're not looking. I've found that a proper barrier for even a week or two makes a huge difference in slowing the regrowth cycle.