I Would repeat Vox's ideas. Also, butter, instead opf marjarine or
shortening, melts really fats. If you are "softening" the butter over
heat so that it is liquid, then your cookies will instantly spread out
into thin crisp crackers. Just leave it out overnight; don't heat the
butter. And for the creaming process, usually combine the butter and
the sugar, and I wouldn't even go five minuites - just a bit so they
are combined. Then add at least a bit of the flour at the end of the
"creaming" for substance.

Then get an oven thermometer to check the accuracy of your oven dials.
Learn your own oven's quirks, don't use dark pans, and still experiment
for the temps and timings that work just for you. Like a laboratory
scientist, keep a notebook or notes in the margin of your recipes.
Note what you changed this time and that, and how the results were.
Practice, practice, and take the results to the office or the
neighbors.