There are 3 dimensions to this answer: 1 - The company has to prove that your skill is unique, and they can't find anyone else. Mostly this is covered by a good description of your qualification and the task at hand 2 - There has to be enough H1B left: Every year, the US issues a certain amount of H1Bs. If they run out, you have to wait for next year. 3 - The company has to be well funded: to prove that they have enough funds to pay you for the duration of your H1B (typically 3 years). If the funds of the company don't suffice for a 3year employment (early start-ups), then you could also apply for a shorter term H1B (let's say 1 year) and then extend once the funds of the company are sufficient.

In any case, I'd highly recommend to talk with a good immigration lawyer. There are many exceptions, alternatives - depending on your country, skill-set, etc.