Yes variants of this question constantly recur, nevertheless I'll try to do a quick and dirty answer before this gets closed.
A single pass over write of the raw drive with anything, zeros, random, whatever is sufficient to make data practically unrecoverable. This can be done via direct write or via the builtin security commands.
Magnetic force microscopes are not going to extract the data.
Wear leveling in Solid State drives would require disassembly and chip removal to bypass the wear leveling controllers. Custom chip analysis of the wear level swapped bits can extract unwiped old snippets but this would be expensive, time consuming and have very little context. Standard forensic shops won't do this.
Bad sectors won't be wiped, but if they are truly bad you likely have nothing significant worth the effort of expensive reconstruction of the bad sectors. Yes, bad sectors can be artificially created to hide data, but if you did this you would know it.
Similarly HPA & DCO hidden sectors will not be wiped, but unless you created them and put data there, there's nothing of your's present.
Official classification standards require physical destruction to avoid even the most unlikely release.
Wipe with zeroes then check for non-zero content afterwards to verify. It won't meet military standards but it's a 99.9% solution.
Since you are looking for a simple "Do This", I suggest Eraser, or DBAN.