Lots of good tips so far!

Glue must be completely dry or will not give good adhesion.

I abrade pretty deeply, until a consistent flat-black appears. A lot of work.

I apply the glue with plastic bag wrap stretched over my fingertip.

And my one particular discovery came when I was studying the "failure mode" some 1990's, rather stretchy and "foam-like" glueless patches, but what I learned applies to glued patches to some degree as well:
The tube should not be in tension from inflation pressure any more than perhaps to round it out, when the (normally stretch-resistant) patch is applied!
Otherwise, as the tube is inflated and conforms to the inside of the tire, there will be continuous residual tension in the rubber surrounding the hole. This is because patches (with the exception of those first glueless patches) are stretch- and compression-resistant, meaning that a stretched tube adhered to a patch will remain stretched in tension. A proper patch prevents the local repaired area of the tube from stretching during inflation!
Having residual tension in the wall of the tube adjacent to the puncture will allow the tube to slowly start peeling away from the patch, starting at the hole where air can enter, then migrating to the outside edge of the patch (creating a complete pathway out of the tube).

Oh and one more thing, that I noticed about 22 years ago, was that at that time many tubes started showing a different material property during sanding. Instead of falling free from the tube, the sanded-off rubber seemed to stick around in little rolled-up lengths of rubber material that seemed "gummy". Adhasion on those particular tubes was extremely poor, and I began tossing those upon first puncture. This reformulated butyl may still resurface from time to time in certain batches. At the time, I thought it might be a plot to force purchasing more tubes instead of replacing, or in today's context maybe forcing us all to use more-expensive tubeless tires. Conspiracies abound.

Certainly also, the glue has become ever less toxic/polluting over the years, and so like most of today's contact cements, not so aggressive at etching into the base surface.
For this dilemma, I use a little more glue thickness upon application, so that the solvents have longer to work before becoming too dry to spread around.
This last technique especially applies to using older, thickened glue (given added work time, the solvents will still do their job effectively!).

That's all I got.