how i can improve my hand grip

squeeze a tennis ball 25 - 50 times a day in each hand and slowly increse this to 100 then more etc

you can get one of those grip things from a sports shop,or like suggested as theres plenty of things in the home you could use,try and find something,good luck,peace.

Do not use vaseline. you have to raw dawg it.

use Talc powder like the NBA uses

if the ball is slipping from your hand, it probably means that the ball is a little too big for you, try to get a smaller ball,and play with that, and later you can change the ball and it will be a lot easier..try to practice grabbing a basketball, you probably wont get it using one hand, but than grab the handball you will see its alot easier..

Hold tighter!