I had problems until I switched to a plastic ball,and learned to roll the ball straight at the 10 pin.For several practice sessions,I did nothing but shoot 10 pins.I believe that this is the best way to become proficient at shooting them.

The ten pin should be the least of your worries. It is the easiest spare to get. That should be your mind set!!! I have an extremely high rev rate so straighter is greater. All it takes to make your most aggressive bowling ball go straight is a slight tweak of the wrist. I literally adjust my thumb from my normal straight up 12 o'clock position to straight forward directly at the ten pin. This slight adjustment in the hand position allows to ball to roll end over end. Mine actually rolls directly over the thumb. thump thump thump thump thump. The ball has no choice but to go straight.

I dont put my fingers in all the way so I dont rip up on it...break my wrist and throw it end over end...also I throw it so it rolls out straight down the lane..I focus on getting the ball to the dry and let it do what it wants to do..roll out in to the ten.

Also...I dont rush it but I don't sit there and think about it..I dont give myself time to think myself out of it...if I am making any sense.   I stay confident, break my wrist and staight ball it down there.  I dont use a spare ball...I like to keep the same feel as my strike ball so I can execute the spare.

Go in for a practice session.  Pick an arrow.  Take a guess as where to stand.  Throw and adjust til you find it.  I personally stand about 12-15 boards left of center (inside of left shoe) and hit third arrow.  i stand 3-5 boards right of center for the 7 pin

Ive been 100% on my 10 pins lately rolling with my plastic ball. I've noticed if I move up on the approach a foot I have earlier timing and can just roll it instead of my usual late timing.

you are working on your release not your approach. Get a few practice games and stand at the foul line and practice pointing your thumb at the ten pin. The only thing holding you back is yourself. So Practice, practice, and just when you think you have it down practice some more.. Watch videos of yourself practicing this motion.. IF YOU REALLY WANT A TRUE CHALLENGE to perfect this release, ask the lane dresser to strip the lane for you. THEN YOU WILL HAVE no choice but to point your thumb at the ten pin and allow the ball to roll end over end or the ball will immediately turn left on you. If you master this, you will never ever have to worry about lane conditions ever bothering your ten pin shot ever again. you can hit the same mark no matter what shot you are bowling on whether it be 1ft or 60ft and still pick up your ten pin. IT IS THE EASIEST SPARE TO GET.

Many people are contradicting themselves in their responses.  Do this, do that, figure out what works for you.  All in one post. 

Many people have had success going to a plastic/urethane ball for their spares, especially for the 10-pin (for right handers).  The theory is by using a ball that doesn't hook a lot by its design, the bowler can use his normal release and be able to hit the 10-pin.  This method does need some practice to know where you need to stand to hit the pin.

But what I have been noticing is even with plastic, high-rev bowlers are having a hard time keeping the ball on track on today's drier THS prevalent here where I bowl.  The excess dry area makes the ball hook past the pin.  What I try to teach is find a line and a release that allows the ball to finish hooking to where the ball is traveling as straight down the lane as possible.  This is especially effective for lower-rev bowlers.  Too often I see bowlers think because they are throwing plastic they can just chunk it down the lane and it will convert the spare.  But you still have to have an approach to the spare. 

Ideally throwing the ball end over end at the 10-pin is ideal, but if you could do that you wouldn't need a spare ball.  So find a release for you that allows the ball to finish hooking by traveling straight down the lane (not hooking back to the left for right handers).  That way if the shot really starts to dry up, you don't have the ball hooking past the pin, but instead hooking TO the pin.