Need clarifications on Mtg ability Rules

Question

I know i'm being a total novice by asking this but I just want to make sure I have all my facts right. If a creature in Mtg have an ability which costs for example 1 G, T Does that mean I can tap it to activate the ability or Do I have to Tap it and tap 1 and G?

Answer 1

The latter.

You have to first produce one colorless mana, one green mana, and then tap the creature in question to activate the ability.  

Answer 2

To activate the ability you must tap 1 and G and tap the card. You cannot choose one or the other you have to do both at the same time.