If you are anything more than a casual site builder then you really should be using Drush. For those coming from a design/visual background working on the command line can seem a little intimidating but it is really very simple and the efficiency and power it offers is huge. From everyday clearing of caches through to complex management of features Drush manages tasks which can take hours in minutes.
Develop on a Page
If I'm adding something very new to my module, I often develop it first in a PHP page on one of my test sites - it's just easier and potentially less disruptive. I still follow the same development "rules" - only the environment is different. If it doesn't work out, it's much easier, emotionally, to throw away a single page than stuff that's already in a module.
Use module filter
To make it quick and easy to find a module (or two), install module filter which allows you to have a search box and grouping on the modules page. Very handy for large sites or sites using a multi site installation.
hook_enable / hook_disable
These hooks are often overlooked but I find them useful:
- Set/reset all your variables to their defaults in this function for an easy way back to an almost-virgin state and to make sure the defaults only have to be correct in one place.
- Provide a message that will direct your users to the settings page.
- Log the userid of the enabling/disabling user.
It's always a good idea to help the end-user, so at least start with a skeleton hook_help. It can be filled in more completely as you go along.
It's a rare module that doesn't have at least one menu item, so go ahead and start with a skeleton for this.
Even if you didn't create any tables or content types that should be cleaned up, I can pretty much guarantee that you used some variables (i.e. variable_get, variable_set). Delete them. If you created blocks, it's a good idea to clean those up too. Don't forget to test it.
Drupal has many more hooks than the ones above. You can find documentation about them at https://api.drupal.org/api/drupal.
To do list
Invariably you will think of something that needs to be done sooner or later. Put a small comment section at the top of your module for including these notes.