... pick ingredients
All ingredients are not the same.  I have a friend that has one of my rub recipes.  They have made it themselves, they can cook, they use quality ingredients, and yet they tell me mine is better.  Why is that?  Because of the components.  I am also willing to allow for the concept that food prepared by others is always better.  :)  I think most of it is the source.  So on this page I will talk about some of my preferences.  Is it the only way?  No.  Is one brand necessarily better than the other?  No.  Many of the choices could go either way, but I built the recipe using one brand and changing midstream would require a change in the recipe.  Let's delve a little deeper though and look at some ingredient options.

Salt
What do you think of when I say salt?  Table salt?  Kosher salt? Fluer de Sel?  Sea salt?  Any one would be correct because they are all salt.  They are not created equal.  Each has their place and they are not interchangeable in my mind.  I haven't bought what most of us call table salt in over 10 years.  I may get a goiter next week and that will be my own fault.  I also do not care.  I have some wonderful sea salt in a grinder that I use on the table and you know what I like about it?  It tastes like salt.  Not metal... just salt.  This is up to you... I am just saying.  There is nothing better than a good finishing salt, like Fluer de Sel, on certain dishes.  For instances I think grilled oysters with butter and Parmesan would be incomplete without a good pinch of Hawaiian Pink Salt.  My Salted Caramels would not be the same without the sprinkling of Fluer de Sel either.  On the other hand a finishing salt should not be used to make a rub.  Cost would certainly be one factor, but texture and the rates at which they dissolve, both on the food  and in the mouth, would be wrong for that application.  My favorite salt for cooking and seasoning meat is Kosher salt.  The crystal size and shape is more suited to seasoning a nice steak or making a rub.  So each has its place and you should try as many as you like.  I probably have 8 different salts in my kitchen right now.  Should you go buy eight today?  No.  A box of Morton's Kosher Salt is all one truly needs.  Just thinking about a homegrown tomato, a drizzle of good olive oil, and a healthy pinch of salt makes my mouth water right now.

Sugar
Sugar is much the same way as there are several kinds of sugar.  White, light and dark brown, sugar in the raw, powder, superfine, maple, and a few more.  They are all sweet to be sure.  How sweet?  How do they behave when heat is applied?  These are the questions.  Powdered and superfine are strictly baking items in my mind and should never be used in a rub.  Now that I have said that some championship team will disclose that they use powdered sugar in their rubs.  Then again, maybe not.  When sugar burns it turns to carbon, which we all know is not good eats, and in general will burn at 350 degrees.  So staying below that temp is critical to not making carbon.  So I can hear you saying as long as I stay below 350 I can use any sugar.  Well, technically yes, but I think there is more to it.  Even though the cooking temperature is low enough I have found that highly refined sugar, white sugar, will darken, or even blacken, significantly more over the course of a long low and slow cook.  This may not be a big deal and it certainly doesn't taste bad, but I prefer browned to blackened in this case.  So brown sugar can work right?  Yes, it will.  Some years ago what we know as brown sugar became a mixture of pure refined white sugar and molasses.  I am from the south and I like molasses on my biscuits as well as the next guy, but adding it to my refined white sugar doesn't change the fact that it is refined white sugar.  I use natural brown sugar in all my rubs now.  You may see it sold as Sugar in the Raw in your local markets.  It holds up to the heat better with turning black and I like that it is less sweet than it's highly refined counter part.

Pepper
There are many types of pepper as well.  Even among common black pepper there is several different grinds.  My choice is to grind my own.  An inexpensive coffee grinder or mortar and pestle works well at producing larger quantities if needed.  A grinder does the job for the table and smaller quantities too.  Tellicherry is regarded as the most "peppery" of the bunch, but even just whole peppercorns from the restaurant supply store or grocery will be better fresh ground than the powders one can buy in a can.  If powdered is your choice just remember fresher is better.

Miscellaneous Herbs & Spices
The same rule should be followed for all of the other herbs & spices.  Fresher is better.  Yes... this means the small bottle of ground nutmeg that was purchased 3 years ago for that one recipe should be tossed and replaced when needed.  Dried herbs & spices are fine to use.  Just make sure they get used in about 6 months or less and replace as needed.  For rubs I don't recommend using fresh herbs, but I suppose it could be done.

In general the components of any dish will have a direct effect on the finished dish.  The seasonings are no exception to that rule.  Pick good ingredients and the dish will follow.