I normally go for 0.3mm but have been known to sneak em down to 0.25mm. The larger is fine. This is for low to medium current, anything greater requires a progressive increase in the hole diameter and a bit more meat on the annular ring. It also depends on the accuracy of your pcb supplier.

If it is single layer pcb, the adhesive under the pad has to provide a lot of strength, so you probably want to go as high as 2mm annular ring or more on a part requiring strength such as a switch, terminal block, coil, etc. If there is not enough room to get appropriate clearances you can use a non-round pad and still get some of the benefit.

At least 10 mils annular ring is better for manufacturability, and a bit bigger than that is even better.

I am doing a new project. Your posting is pretty good and useful to my job.Thanks a lot. Hope you can write again.