Never use a feature anywhere unless you're ready to use it everywhere. For example, EIP.
In a browse only show the fields that uniquely identify the record. Everything else is a hot field.
UI advice: don't create ransom notes!
Use themes. They're also a good starting point when you talk to a new customer. Use the ThemeMaintenanceWizard utility. Greg went through a number of his preferred theme customizations. You can also change the procedure naming convention.
Drop lists for sort orders take up less space than tabs and don't scroll off the page or stack up.
Make your buttons large enough so they can be a uniform size.
Change the text prompts to what you want. Keep your verbiage standard.
In the dictionary you can specify which tab a field should be on.
There's an amazing amount of customization possible in the theme wizard
Greg has a Button Combiner template he will be posting on DevRoadmaps for CIDC attendees.
Change default object names to something memorable.Same for queues and FEQs.
And many more tips, of course.