When in doubt, here's a list of standard practices to follow in UI design. None of these are set in stone.

1. Design for density, not pixels

Design for the pixel density of the device, not raw pixels.

2. Use 8dp increments

Spacing in increments of 8 creates consistency across devices.

3. Remove lines and boxes

Boxes and lines dividing content could often be replaced with margin.

4. Pay attention to contrast

Contrast draws the user's eye and improves accessibility.

5. Familiarity is good

Be creative only within the confines of current design norms.

6. Use color weight to establish hierarchy

Assign different levels of importance to elements using color weight.

7. Avoid using more than two typefaces

Two typefaces (with families) is usually enough.

8. Recognition, not recall

Minimize the user's memory load by making objects and actions visible.

9. Don't slow me down

Be purposeful with animations; don't add unnecessary delay.

10. Less is more

Every added element competes with the relevant information on a page.