Here's a useful 3D printing trick I picked up from Maker's Muse:

When 3D printing something that has a hole parallel to the XY-plane, you'll end up with a flat or drooping spot in the "ceiling" of that hole.

To remedy this a teardrop shaped cutout can be added to the top portion of the hole. With this method there's no need for using overly loose tolerances.

I found that an angle of 100°-120° at the edge of the teardrop works well.

Maybe this is common knowledge, but it was new to me so I thought I'd share it here.

Well, that's all for now.