The simplest method is to use a staple gun, such as the Stanley 2in1 Cable Staple Gun model CT10X which can use a rounded head staple.
Staples are shot in about a foot apart, and pried slightly up to easily feed the tube through so it is not pinched at the staples. This will keep the tube neatly in place. For sections between the house and a hanging basket stand, for example, the tube could be run in the ground in a shallow trench and covered over out harms way and out of sight. If you do bury the tube in places make sure that it is not in a place where a flower bed, for example, might be turned over with a spade, thus running the risk of damaging the tube.
It is difficult to shoot staples in to secure the tube after the tube is already in place, so a certain amount of planning is needed so that there are staples where they will best keep the tube in place. It is a good idea to have a staple located near a Tee to secure it at that location.