- add 'copyright' file: provide description of your license. Do not include it's full text into the file, write some reference to '/usr/share/common-licenses/YOUR_LICENSE' instead;
- check 'control' file: dependencies, description, long description, etc;
- check 'changelog' file: pay attention: follow a very strict format. It may be useful to store changelog permanently inside your package directory.
If something is wrong with formats or whatever, lintian will tell you during package check.
Make sure no errors (E) show their heads. There may be some warnings (W). Look through lintian tags and check their 'severity' and 'certainty' attributes. Your warnings may be not significant, such as 'new-package-should-close-itp-bug'.
You may also sign your package with your PGP key and put it to some PPA.