The FAQ answer that here. However I do not seem to attract trolls from exactly the same actions mentioned in the FAQ. Instead, collecting from the following stuff brings troll to me:
Coin buildings: Royal buildings, all character's houses (Old Thomas, Ivy, Thurston, Sabina), Windmill, Tavern
Special stuff: Tablet, Troll Pit, Magic garden (can't say about the Roost)
Resource buildings : both kinds of mines and Wizard school (instead, stables, hatcheries and sawmills attract fangbeasts), plus Glimmerdust Trove
All mushroom except fluttermush ring, from the V-day edition (because it attracts lovecupine)
Mining rocks may work but they might attract skunkupines and fangbeasts too
Crops: Cabbages, Glimmerbulbs, Cocoa
All this works better if you collect very fast from a bunch of this stuff in a row, ie click to collect from all your Royal buildings one after the other, or try to collect 20 glimmerbulbs/cocoa/cabbages... most likely, a troll will pop up and interrumpt your game