Does anyone have any useful tips on how to get your dog to drop the toy when playing.  Bess is territorial and thinks it's fun to stop me from getting the toy from her.  I see people in the fields playing fetch with their dog and would love to do it with Bess but just know that if I took one of her toys and threw it, she would fetch it but wouldn't let go of it.  Any ideas would be appreciated.

I've always done a "swap" with something of higher value, i.e. a tasty treat or another toy and used the command leave or give.

I did eactly the same as the person above me recomends.Replace the toy with the offer of a "Swap" coupled with a command word that the dog associates with it.
Then once the dog gives up the toy reward it with lots of praise...it works for me.
also if you dont always want to use a food treat when giving up the toy,once the dog has got the general idea just increase the time between the dog giving up the reward and the treat for doing so then start altenating that with just vocal praise so eventually the dog will give up the toy with just a vocal command and vocal praise.

As well as 'swapsies' you can adopt the strategy of once she has let go immediately engaging with her in a game with the toy - bring it to life so that it is much more exciting that when she has it on her own.  Then decide to end the game of tuggy or whatever when you are ready and her reward for letting go becomes yet another game with you. 

I do the same as Gunner. With small pups I make the toy really lively and fun then freeze and stop moving. The pup usually lets go then I immediately reward it with a "good dog" and making the toy lively again and more play. That's one way I introduce the drop command. With swaps I don't usually take the toy away permanently. I offer a treat with a leave command, dog drops the toy, gets the treat then - wey hey, gets the toy again! Great game for dogs and they learn that I'm not always out to take things away from them. They'll bring their most prized finds to me because I'm safe.

With Bess start in the house or garden and don't let go of the toy. Just play some tuggy for a few seconds. Then become boring and if needed offer a treat. As soon as she lets go, "good girl" then play with the toy again. When she's good at letting go you can try letting her have the toy. If she runs off don't chase her, try running away from her. She'll probably chase you instead. When she catches you have a game again. I do chase my dogs in fun but ham it up - do monster walks, silly runs or say "I'm going to get you" so they know I'm playing and want them to run.