One of the most frustrating things as a beginner gardener is distinguishing whether a seedling is that plant that you planted or whether it is a weed. I would always upload photos to 'Name That Plant' of tiny little seedlings, asking for help in identifying them. Problem is -- lots and lots of plants look exactly the same before they are distinguishable. The kind gardeners at Gardenweb just ignored me when I asked such ignorant questions, and I finally started to figure out the way these things work.
You see, there are seed leaves and true leaves. Once the true leaves show up, IDing a plant is much easier. You don't get true leaves at first though. You get seed leaves. Seed leaves are quite literally the leaves that emerge from the seed. There are usually two and they extend in a 180 degree angle from each other. The plant uses photosynthesis from those little leaves to grow a solid stem and roots and then starts putting out true leaves that are miniature versions of the mature plant. Can you guess what this plant is below based on the true leaves?
So new gardeners, my advice to you is simply to wait. Give those seedlings time and don't weed until you know what everything is. Grow plants in pots so you get used to their germination and growth cycle. Then plant them in the ground and wait...just wait until those true leaves appear. Then you'll know what you are dealing with and can weed effectively. There is nothing like weeding your greens and ending up with a bunch of violets still in the ground and all your spinach seedlings weeded out. No good. So be patient!