DO consider at least one variety of a subway tile (even if you think it’s boring). This can be the classic 3×6 or something closer to 6×18. Boring now = timeless later.
DO go with a colour that relates to your kitchen. If all else fails, stick to a white.
DON’T go with a trendy mosaic.
DON’T choose a busy tile with a natural stone counter. The only time you can consider (with caution) a busy tile, including any form of mosaic, is when your counter is a SOLID quartz.