Head out towards the airport (through the Fortitude Valley) and follow signs to the airport. The on-ramp onto the motorway in Hamilton is a good spot, too.
In 2018 the easily hitchable towns going north up "The Bruce Highway" from Brisbane are: Tiaro, Childers, Gin Gin, Miriam Vale, Bororen, Benaraby, Mt Larcomb, Marmor. Rockhamptonwas a little more difficult as it is bigger but still no problem getting to Mackay. (we didn't go further). At these places the traffic slows and there is room to pull off. Anywhere else on the A1 is going to be more difficult.