The first. Weighted straight arm lifts help to strengthen the pathway that the arms take under load when pressing or jumping into a handstand.
The second. Handstand Pike walks. Basically here we are repeatedly doing reps of what is generally speaking the hardest sticking point in a press handstand. If you find that this exercise is above your level of flexibility, split the legs to a wider straddle. If you find that this is above your level of strength, simply lean as far as you feel comfortable over the wrists, and push as hard you as can for 5 seconds without trying to brings the legs to the hands for reps
The third. A-frame push ups. If you want to make your arm balances and chatarunga feel like a stroll through the clouds this is for you. Its also great for those wanting to start developing the strength needed for free standing handstand push ups. Can also be done with the legs straddled if your a tighty.
Try three to five rounds of each once per week consistently and watch your handstands improve.