If you owe a genuine expression of thanks to someone who really helped you out and made a difference, "Thanks so much!" probably doesn't get the job done. Instead, try hitting three important areas.
Be specific and reference the thing they did for you.
2. Explain why you're appreciative.
This should ideally be about them, not about you.
3. Reiterate your appreciation by pointing out the difference they made.
An effective thank-you pays the person back in some way, it makes it more likely they'll help you in the future, and most importantly, it's just the right thing to do.