There are 2 types of tribute now.
Personal (GoD) and Guild (OoW).
Personal tribute works by donating items and/or coin to your Tribute Master in your hometown. You build your Favor Pool this way.
You then pick what you want as effects from the list. Several of them have different Tiers which are level restricted. Each tier progressively costs more Favor. When you pick what you want, you will see a total cost in the bottom of the Tribute Window (Alt-U). This total amount of Favor will be the amount deducted from your Pool every 10minutes that Tribute is active. When you click activate, this amount is removed from your pool. 10 minutes later, this amount is removed again, 10 mins later....and so on.
The amount is removed at the BEGINNING of the 10minutes and the timer is refreshed if you ever turn them off in the middle. The timer does not run when the character is logged out.
Effects include: All Focus effects I-IV, Haste (worn, up to 41%), FT I-V, Regen, Vengence, Stat boosts, Resist Boots, See Invis, EB, UV, Faerune, and a few others I'm sure. You can have up to 4? (I think) effects running at once.
You will need to return to your hometown tribute master to modify the effects, but not to turn them on or off.
Guild Tribute works by donating items or coin to the Guild Tribute master (one is located in PoK for sure, not sure where there are others.) This system works much like the personal system, except that only officers and above can modify the effects given. Any member can donate for favor though. Members can "Opt in" and "Opt out" if they wish to receive the effects. The timer runs while anyone is "Optted In" and online.
Effects include - most of the personal tribute effects, FT/Regen/Vengence, Haste/Spell Haste/Double Attack+, HP/Mana/End, and a few others. I personally like the combination ones and will be runnign FT/Regen/Veng and HP/Mana/End for the guild. You can only have a max of 2 effects for guild tribute running at once.
I am not sure how (other than visiting the tribute master here) to turn these on for yourself. You can Opt out at any time though by hitting the Opt Out button on the guild management window (There's a tribute tab now), or on the guild tab of the tribute window.