The best way to say 'Can you help me?' in Spanish is the following: Puedes ayudarme?
Puedes: is a form of the verb 'to can'.
ayudarme: is a form of the verb 'To help'.
This is the most common way but if you need to use a more formal way yo must then say:
'Podria usted ayudarme?'
'Usted' meaning 'you' when you need to talk to someone in a formal context (e.g.: policeman, teacher, etc).
You can also add 'por favor ' that means 'please'
Can you help me please? - Puedes ayudarme por favor? / Podria usted ayudarme por favor?