Planeswalkers

[raharu]

I can Stifle/ Trickbind/ Pithing Needle them, right? They are activated abilities, correct? The tokens are the cost, and the effects encompas everything to the right of the colon, if I understand correctly.

[jazzykat]

While we're on the subject, when do you have to say who you are attacking. I attack with goyf on an open board and want to kill Jace?

[Taurelin]

I can Stifle/ Trickbind/ Pithing Needle them, right? They are activated abilities, correct? The tokens are the cost, and the effects encompas everything to the right of the colon, if I understand correctly.

"Counters", not "tokens". But apart from that: Yes.

212.9f Each planeswalker has a number of activated abilities. ... The cost to play an activated ability of a planeswalker is to put on or remove from that planeswalker a certain number of loyalty counters, as shown by the loyalty symbol in the ability’s cost.

While we're on the subject, when do you have to say who you are attacking. I attack with goyf on an open board and want to kill Jace?

In the Declare-Attackers-Step.

308.1. As the declare attackers step begins, the active player declares attackers. This game action doesn’t use the stack. If the defending player controls any planeswalkers, or the game allows the active player to attack multiple other players, he or she declares which player or planeswalker each creature is attacking.