However, are there any hints you had in mind when you wrote "how to use GPS effectively" that I can consider next time I fly?
I know you're not asking me directly ;-) but here is my opinion.
If you use GPS, I think before you get in the plane, make sure you know how it works, or at least the parts you are going to be using. What I mean is that if you find yourself lost or in controlled airspace, then a) it helps to have avoided that when planning on the ground, and b) if you think your GPS is giving you wrong information, its best to abandon it and get on with flying the plane than having your head down fiddling with knobs or touch screen buttons for ages.
Another exampe: I am fully comfortable with SD now, but as an VFR /IMCr pilot, I am not fully conversant with my Garmin GNS430 in terms of IFR procedures. I know how to use the FPL option and the Direct to and a few others bits and bobs, and I have flown one hold and one ILS approach using the GNS430 as backup. While I did that with a safety instructor, and while I have a GNS430 trainer on my PC, I would be foolish to shoot up into the air and think I could do any ILS approach at any airport without further on the ground planning or forethought.