How can I identify sores/lesions on my lip, tongue and gum?

See professional. The best way to get an accurate diagnosis of the sore or lesions that you have is to see a dentist or oral surgeon for an examination. Some lesions need to be biopsies for diagnosis.
Not DIY. Your dentist or the oral surgeon he/she prefers have years of training and experience in identification and treatment of oral and peri-oral lesions. Please make an appointment for examination and, if necessary, treatment.
Proper diagnosis. Are you an oral pathologist? Oral surgeon? Ent specialist? General dentist with oral diagnosis training? If not, i suggest you leave it up to one of these professionals for a proper diagnosis. Merely reading information and looking at photos on the internet will not enable you to properly diagnose oral lesions.