I will tell you how to make a successful Minecraft map 

1.
Start Building
you don't want the map to be to short or to long 

2.
ALWAYS have a story line and have something happen in the map Example: My story line will be, A long long time ago in Makariku Village lived a young boy named Clark until one day Clark was missing we found out that Clarence Kidnapped him! and what happened? Clarence kidnapped Clark to make him into Clark Stew.

3.
Make the map fun
Make other people have fun playing you're map 

3.5 
This Goes with #3 
Add some mods in the map if you want to make it funner! (ONLY If you want)

4.
Spell everything right 
You want to spell everything right so they can understand what you are saying (Signs/Books)

5.
Make the map look beautiful you don't want it to look dull unless if you are making a Horror map.

5.5
Something that goes with #5 is you want a Texture/Resource Pack this will edit the Minecraft blocks/items just the way you want them to be, Example: Edit Oak Wood for Blue Wood

6. Play through it to see if everything's right you don't want to get lost in places or say "Where do I go now?" make any edits to the map if something is wrong that's why I recommend a guide telling you where to go next (in a book will be easiest) 

7. 
Record the map so people can have a preview of it before it comes out only make a short trailer of it.

8. Make the map public by using MeadiaFire or other Programs 

9. 
For you're map to be popular PM a youtuber and see if they will respond back you don't want to spam them cause then they might block you. I started with Bodil40 with my Parkour map.

9.5
Goes with #9 You don't want to start with a Famous youtuber like the Yogscast, I started with Bodil40 and I will slowly ask other people like AntVenom. Slowly meaning not going to Bodil40 then going to The Yogscast right away.

10.
If you want to make edits to the map to make it look better then do so, but then you will have to do step #8 over again and you will have to remember to change the download link on Planet Minecraft, or any other Minecraft map posting websites.