Observe, Identify, Research possible uses, then Determine disposition.
This time of the year -- just getting ready to plant out tomatoes but still gets down to borderline 30's once in a while -- some areas in my yard are full of Garlic Mustard in their 2nd year bloom and Ground Ivy also in full bloom.
Both are considered weeds. But with the mustard in bloom, I see arrival of my aerial Garden Patrol -- syrphid/hover flies, nemesis to aphids. Hopefully braconid wasps are not too far behind because my broccoli and cauliflowers need their protection from the Cabbage worms. The Ground Ivy flowers start to buzz with early native ground and mason bees, giant queen or overwintered bumblebees and carpenter bees, as well as early honeybee scouts.
I also have volunteer apple trees, cherry trees, holly bush, elderberry,... well you get the idea.
If they are growing where I don't want them, I'll move them or if I definitely don't need them, I'll cut them down. But most things get to grow until they are identified.
In the garden beds, I also have lettuce volunteers as well as Red and Green shiso and Japanese parsley, Dill, Cilantro, Tomatoes, Borage, Calendula, etc. -- all the self-sowing stalwarts. They are moved if necessary or allowed to grow until micro-green size if edible. Tomatoes end up mostly pulled but I let a few stay.
Tomatoes also volunteer in my home-made potting mix, and I always end up with at least one winter tomato (DD is enjoying the grape tomatoes that have ripened in the kitchen windowsill now) and I have a tomato plant that is hardening off to be planted that has much darker/blue-ish green leaves and purplish stems. I've no idea what this one is going to turn out to be.