I paint the baseboards, then tape them off, then paint the walls. Tape is the only way to get a perfectly straight line, even though there are still plenty of pros out there freehanding and calling it perfect when it's not. Use blue tape and be sure that back edge of the tape is pressed firmly down or paint will bleed behind the tape. I use a flex blade to do this and I have a very tiny screwdriver that I use in corners.

I have already painted the wall. If I put blue tape on the freshly painted wall, then paint the trim, will the tape likely pull the paint off when I remove it?

It depends on if the drywall was primed initially when it was new. I try to stay away from taping off walls for many reasons. In your situation, I would probably paint the baseboard, then tape them off and touch up the wall where you got trim paint on the walls.

Frogtape and Edge-Lock always work best for me.

I always paint the baseboards first, let them cure for 24 hours, tape and cut in along them. Since this isn't a production job, preparation time isn't an issue.

For a perfect job, you'll need to remove the baseboards, paint, attach, putty nail holes and caulk the gap. Hardly worth it.

I have never seen a "perfect" paint job, no matter how it is done. Brushworks said it best in the last post

What?

perfect
entirely without any flaws, defects, or shortcomings:

not gonna happen with ANY painting job

Okay, I get that, but how does pulling off baseboards and re-installing them help?

I would guess, no wall paint on the base and no base paint on the trim?

Follow up question - why not paint the walls first and then the trim? That would allow you (at least for the baseboard which is most of the trim in my house) to tape off the higher area and paint the lower area. This way gravity is less likely to pull the paint down and under your tape.

Well, it's the same issue as always. The gap between the wall and trim needs to be caulked. That caulk needs to be smoothed out with a wet finger. Since you are bridging a gap here, and you need to paint over the caulk, you now need to paint the wall and the trim. This is something that can't be done prior to installation. I think it is totally true that there is no perfect paintjob, but I do believe that you can paint your baseboard, tape off the baseboard properly, paint your walls, pull the tape and be left with a perfectly straight line when you are done. Anyone can do it. It's just a matter of putting the tape on properly.

Follow up question - why not paint the walls first and then the trim? That would allow you (at least for the baseboard which is most of the trim in my house) to tape off the higher area and paint the lower area. This way gravity is less likely to pull the paint down and under your tape.

Dave, you should go ahead and try that. It may come out fine. The reason I tape off baseboard and paint the walls last is because that is the way I have figured out over the years to have the best final result. It's not so much gravity that makes paint bleed under tape. It's mainly user error ... in other words, the person putting the tape on doesn't push that back edge down. Another way to get bleed is by brushing the paint too much and actually pushing it behind the tape with the bristles of your brush. You may find in the end that taping off a wall over your baseboard that it's not easy to make the tape straight this way. All you can do is try it out.

High quality caulk, like DAP 230, elastomeric does not require painting if the color is acceptable.

I have a new build house that is almost 3 years old. I used brilliant white DAP 230 around base, jambs, etc. Still brilliant white.

If you're using a cheap diy product like Alex, then you better paint because it does not seal out environmental dirt and will yellow in weeks. Or if you have a dirty house, pets and/or lack housekeeping skills, paint the caulk to make it more resistant to dirt.