Tip: See my list of the 
MostSentences with the verb “look” (in the sense of “appear, seem”) have a different structure from what many English learners think. “Look” is followed by an adjective, not an adverb:
correct She looks pretty.
wrong She looks prettily.
correct It looks large.
wrong It looks largely.
However, we run into another problem in the case of “good” and “well”. “Well” also has a second meaning, “in good health”, which is used as an adjective. Therefore, both sentences below are grammatically correct:
correct He looks good.
correct He looks well. (But it means something else!)
The meanings are as follows:
he looks good = he is good-looking
he looks well = he seems to be in good health
he looks well = he seems to be in good health
If we use “look” in the sense of seeing or searching, then “look well”, where “well” is an adverb, makes sense. For example, we could say:
If you look well, you will see it.
This construction is possible, but “carefully” is more common in this context:
If you look carefully, you will see it.
