Ugly edges

I am working in stockinette and my edges look really bad. They are loose and uneven. I am going to need to pick up and knit both sides and right now I can’t tell what to pick up. Are there any tips to make my edges look neater? Thanks in advance.

If you’re going to be picking up the stitches for a border it’s best to leave them just knitted.

Should I knit just the first stitch of each row or the first and last stitch of each row? How can I tighten the stitches up?

You can just keep the sts in the pattern, either knitting or purling however the row is set up. Work the first st, pull the yarn lightly, then work the next couple sts a little snugger. That can make nice even sts at the edges.

if you want to pick up the stitches anyways: mostly you are not supposed to pick up one stitch for every row. Check your pattern. Often it says to pick up a certain number in total or 3 stitches out of 4 rows (common).
so if your edge became uneven: don’t bother too much. Just make sure there are no gaping holes anywhere afterwards.

For nice edges I knit all my stitches (or purl them, what ever is required) on stochinette pattern. Just work the first few stitches a little tighter or pull them tighter afterwards, if needed.

if you do not want to knit onto the edge / pick up / sew together… then look up all those beautiful edges with little bumps, chaines, etc. But for you current project: just work all stitches and try to stay even an rel. tight.