Look for indicator words within the clue. Anything that suggests a mixture or rearrangement can be used and there are hundreds of possibilities. It may be as simple as :
Amend a mixed diet (4) = EDIT
Be aware that the anagram may not be made directly from the words of the clue itself - you may need to solve something first such as:
New American shoe dwellings (6) = HOUSES (anagram of US + SHOE).
The anagram indicator may not be as obvious as the above examples. It could be anything that suggests a combination, mixture, rearrangement etc.
Here are some examples from the accross clues in yesterday's DT
11a It's cheap, awful potpourri. (8)
13a Hated fine art display of spiritless nature. (5-7)
16a Purposeful precautions I put in place. (12)
21a His descendents left no traces sadly (8)