i always slice the meat across the grain(you can slice with the grain, but run a higher risk of chewy jerky). slice when semi-frozen for ease of slicing and consistent results(especially since you'll be slicing across the grain). it'll shrink some, so slice just a hair thicker than you want the final product to be(slice too thin and it'll fall apart, slice too thick and you may be chewing more than you want). this may take some experimentation(especially if you make jerky from different meat sources). i can't really tell you a specific thickness to use because slicer adjustments vary, but i usually do mine pretty thin(enough that it holds together once sliced). once sliced, marinate at least overnight. don't crowd the trays(allow space between slices for airflow). rotate trays every 60-90minutes(easiest way is to move bottom tray to top each time). dehydrate in batches(ie-wait until one batch is completely done before starting the next). and leave the meat in the marinade until you place it on the tray. within each batch, some pieces will finish before others(usually the smaller ones), pull off each piece when it's done even if there are more going. before packaging, allow time for the meat to cool or you'll have condensation in the package which will ruin it quickly. package in portions you wish once cooled to room temp. repeat until done.
as for a marinade recipe, here's what i do(no measurements as everything is to taste)
marinate slices at least overnight in a mixture of
soy sauce
worcestershire sauce
teriyaki sauce(the thin stuff, not the thick kind)
garlic powder
black pepper
crushed red pepper
brown sugar or honey
citrus juice(lemon, lime or orange)
mustard(dry or prepared)
you can add or subtract from this as you wish to suit your tastes
if you want more heat in your finished product, you can adjust the heat to your taste by adding more crushed red pepper or some cayenne powder or some of the hot sauce of your choosing.
if you don't want any heat, leave out the crushed red pepper and don't add any other heat sources. but leave the black pepper in.