This section is more applicable for time trials where speed is paramount, and the levels are generally a bit less tricky, but these are good rules of thumb anyway. Unlike the “do not create 2 ends” rule, these are not always correct.
Work Outside -> In
The general idea here is that when you have a big blob of tiles, the easiest way to avoid getting stuck is by doing circles around the edges first, then working towards the centre.
A related idea is to keep things as round (or square) as possible, and have just one blob of tiles. This is an aesthetically pleasing and easy-to-follow way to reduce the chance of creating extra ends, and otherwise identify problem areas where you may be forced to create an end.
Clear Red Tiles First
When I see big blotches of red, I like to go only red first, unless it conflicts with the general idea above to work outside -> in. The idea is that by removing red tiles, you simplify the situation, making it easier to see what you should do next.
Be careful with this general idea, and try to keep it localized. Always prioritize the first rule of thumb, working from the outside in and keeping round/square shapes. Personally, I like to combine the two, where I clear all the red tiles along the outside first, work outside -> in, then clear the next set of outer red tiles, rinse and repeat.
Below is an example putting these rules of thumb into work, on a random level: