Formal:
* Muchas gracias: This is the most common and polite way to say "thank you very much."
* Muchas gracias de antemano: This means "thank you very much in advance" and is used when expressing gratitude for something someone will do in the future.
* Le agradezco mucho: This is a more formal way to say "thank you very much" and is used when addressing someone with respect, like a professor or a boss.
Informal:
* Muchas gracias: This is also a common way to say "thank you very much" in informal situations.
* Gracias de corazón: This means "thank you from the heart" and expresses sincere gratitude.
* Mil gracias: This literally means "a thousand thanks" and is a more emphatic way to say "thank you very much."
* Muchísimas gracias: This means "very many thanks" and is a more emphatic way to say "thank you very much."
Other options:
* Te lo agradezco mucho: This means "I thank you very much for it" and is used when expressing gratitude for a specific thing.
* Estoy muy agradecido/a: This means "I am very grateful" and is a more emotional way to express gratitude.
The best way to choose which phrase to use depends on the context and your relationship with the person you are thanking.