I have a small wildflower area in my yard and usually I just throw the seeds out there. This year however, I raked them in a little bit and noticed they came back better (probably because the birds had a harder time finding them for lunch.

Weed competition is always an issue. I would knock back the undesireable plants a bit before sowing seed.

The plants you want will self seed as will the ones you don't want. I would suggest pulling the ones you don't want (or at least cutting down before they seed) and leaving the ones you want. Learn to recognize seedlings or early spring appearance and pull the unwanted as early as possible.

Over time, the wanted will outstrip the unwanted.

One approach is to grow plants in pots until they are reasonably large, then clear small areas to transplant groups of potted plants. This will give the plants from the pots a fair chance to become established before the surrounding plants fill back in. Once established, many wildflowers like Milkweeds, asters, sunflowers, etc. will persist for years or even spread on their own. I think simply scattering seed in a field is unlikely to work unless the seed has a bed of cleared soil in which to grow.