He told teenagers at Tom Hood school, Leytonstone, how he went from being a failing pupil to landing himself a pound;100,000 job with self-made tycoon Alan Sugar.
He described his experiences growing up in a one-parent family and how he overcame poverty and racial discrimination.
The 28-year-old former transport manager for London Underground said:
"Always walk with your head held high. Nobody is above you. I went to a meeting just the other day with a big executive company chairman. I walked straight in there, marched over to him and firmly shook his hand while introducing myself. People will always remember you if you do that. Do not cower in a corner. Make yourself noticed and be confident - whoever it is you're meeting."
Tim battled against 13 other contestants for the job with Sir Alan throughout the first series of the BBC2 reality show. His prize was to be appointed as project director at Amstrad, part of Sir Alan's multi-million pound empire, where he continues to work to this day.
He told the students: "I had a difficult time at school and started bunking off and playing around in lessons. Then one day a teacher took me aside and said, 'You're in control, not us. If you want to make something of yourself, you'll have to buck up your ideas'. That is when I realised that teachers only want the best for you, so seize the opportunities they offer you."
Aaron Clarke, 15, said: "After listening to Tim, I'm really going to pull my socks up. I enjoyed it because it was realistic and not fake like some talks you hear.
"I spoke to him about a dance school I want to set up, as I'm really interested in street dance, and he gave me loads of advice. He said I have to be committed to what I do and also to broaden the type of stuff I offer."
His classmate, Anja Mizdrak, 15, said: "Tim spoke so well - it was really inspiring. He was so down to earth and approachable. I went to shake his hand, as he said it was really important, and he was really impressed with mine.
"He said it didn't matter what we want to do as long as we work hard and finish school, the options will be open to us later on."
After the speech, Tim spent over an hour with the students, talking to them individually about their future and what they wanted to do after school.
Radhika Bynon, a teacher at the school who organised the event, said: "He was interested in each and every one of them. He really encouraged them and has made a huge difference. It was music to the teachers' ears."