Make sure your basics are there and that you are actually ready to start working towards your one arms. While some one arm drills are extremely beneficial already when working towards your very first freestanding two arm handstand you can only truly benefit from the one arm training when you are actually ready. A question that I get quite often is for how long someone should be able to hold a handstand before training for one arm handstands. Unfortunately you can not measure it quite that simply. Instead of taking endurance as a criteria one should look at control, alignment and awareness. 

A good sign that you truly are ready to start focusing all the way on one arm handstands is that you can do single leg isolations without bending the elbows to catch your balance. This shows that you are able to coordinate your legs and body upside down while staying strong and stable in the shoulders which really one arm handstands are all about.

The obvious part is that when we are standing on 2 hands each of our shoulders carries half of our body weight. The not so obvious part is that as long as we are standing on 2 hands  the weight mainly goes on the inside of the shoulder. As soon as we transfer over to one hand not only does this shoulder now have to carry twice as much weight but also does the weight travel towards the outside of the shoulder.

The 2on2 handstand or handstand with narrow hands is a great starting point. Start at the wall with slide aways before training them freestanding. Besides preparing your shoulders on a strength level your body awareness and coordination will improve. You are feeding multiple birds with 1 single scone 😉

You can use wooden handstand blocks. Simply place them next to each other and close the gap. If you do not have them train on the floor with your hands as close towards each other as possible.

Last but not least, take one block away and start working on the Miami Handstand. I call all handstands when you have 1 hand elevated on blocks and the other on the floor Miami handstands because I love Miami, I love those drills and I came up with most of them at South Beach.
For now the idea is to keep the block elbow bent so that both shoulders and hips are parallel to the floor. You should have equal weight between both hands and your hands should be shoulder width apart or less.

You can either use your wooden handstand blocks or really anything similar to elevate the hand. Yoga blocks, tupperware or a pile of books will do here.
If you have difficulties getting up at first head over to the wall and practice slide aways and simple take offs from the wall. Work on getting used to this new hand and shoulder position, You will quickly realize that the only truly tricky part here is jumping into the position. Once up and aligned the basic Miami Handstand is almost just like a regular handstand.