What are the usual signs that a person has diabetes?

Richy is awesome!!!! asked:

I went to my GP yesterday as a follow-up appointment after being diagnosed with cellulitis in the foot. A number of other concerns were raised about my circulation and my heart which were showing some bad results after checking blood pressure. They said I am also very low on oxygen due to shortness of breath. I am going for some tests on Monday and Tuesday to find out whether I do have diabetes and anything else but what are the usual signs that a person has diabetes?