I lay in the floor on my side, either left or right side. If I am laying on my right, I place the left hand on the floor with my fingers parallel to my body. My right hand is adjacent and in front of me with the palm placed on the floor. and keeping my body straight I pull myself up until my arm is in a 90 degree angle. Then I switch sides.
I also use the common trick with the chair. I grab a chair, or a bench and I place my hands on the edge of the chairs facing forward. Then I move two steps to the front of the chair and I start to lift my body up with triceps. Is kind of hard to explain, lol