Google maps. Just look for creeks feeding the lakes and you can see access points on them. I have spent hundreds of hours scouting out creeks this way. You can also see laydowns or stumps too depending on the lake level at the time of the image.
I pulled up Grapevine and circled what I see as creeks. I guess you just have to find some you can get to.I can take the boat and bank it and walk up into the creek if possible. That is, if I cant get the boat in up in it