Here is a list of Dos and Don'ts for creating and uploading Resource Packs

DON'T
1) Improperly zip the file.
To make the game read the file, the root folder MUST contain the following:
- the "assets" folder
- the pack.mcmeta file
If these are not present in the root folder, then the game won't even display the pack in the list.

2) Do fancy stuff in the .mcmeta file.
First, I'll admit there are legit reasons for messing with this, and the custom fonts are cool. However, I've seen too many packs not work due to broken .mcmeta files. Therefore, if you don't know what your doing, then stick to the basics; a simple description and the version number.

3) Include unchanged assets.
Unchanged assets are things like textures and models that were not modified in any way. These eat up space and cause unnecessary conflicts. Plus, PMC actually lists this as being against their rules. Just don't do it.

4) Use shady or somewhat malicious sites to post your packs.
You want to receive a little pocket change for your work. I get it. However, by using a malicious site to host or link your file, you are putting the users of your pack at risk. This will hurt your reputation, and then good luck getting people to download your stuff. Plus, how do you know that site won't hurt you when your uploading your file or creating your link? Also, other mod related sites actually treat this as a bannable offense.

DO
1) Test your pack before uploading it.
Let's be honest here. The first two things on the Don't list wouldn't be worth mentioning if everyone just tested their packs first.

2) Include something like "Unzip Me" in the name of files that need to be unziped.
Sometimes, packs that work together get put into a single file, and sometimes people forget they have to unzip that file and need a reminder.

3) Organize your stuff.
Separating all the things into groups can make navigating the pack easier and faster. Plus, it becomes easier to identify the new stuff from the existing stuff. Trust me, you'll thank me later.

4) Optimize your models and textures
To increase performance and reduce file size, it's important to remove any unneeded data from all models and textures.
Texture Optimization
Model Optimization