Bad ground?

[85square]

Before i put my truck away for the winter i was having some issues that seems like a bad ground to me and want to fix it when the nice weather comes around. I've read some threads with similar issues but figured i would confirm that my issues were a bad ground. When i use my left blinker, the light stays solid and does not blink. When i turn my high beams on, one low beam goes out and the high beam diagonally across comes on. And most recently, when i go to start my truck the starter will engage off and on or won't engage at all. I have a fairly new battery in it and have had it tested so i know its good.

My question is, do you guys think this is a ground issue? If so where should i start to fix the problem? Is there a list of ground wire locations that i can clean? I hate electrical.

Any help is appreciated, thanks!