Shooting lighting is not about shutter speed. It's light and short enough to render sharp regardless of the shutter speed. It's pretty much like a big camera flash.
Set your ISO to the lowest value as you would for a typical landscape. You'll have to figure out what aperture works best for you, but I'd suggest starting with something like f8. I assume you were shooting with your 50mm 1.4. Going wider won't hurt, try something like 24mm. Now there are 2 ways of shooting lightning:
1) Get your tripod out of the closet and mount your camera. Remember to set your focus. I suggest to do it manually, if you're using a wide lens and f8 just set it short of infinity and you're good. Also make sure to have the IS turned off as it can make a mess with the camera on a tripod. Set the shutter speed to 30s and fire away hoping you'll get a nice lightning in your photo. If not - try again. Shoot till you succeed. Remember that with such a long exposure you will be getting a lot of ambient light in your shot, meaning you have to also keep in mind a nice composition of your foreground. You don't have to shoot at 30s though, you might try bulb mode if you want to. It all depends how much light you have in your foreground.
2) This is the way I usually do it, especially if I don't have a tripod with me. Shoot handheld. As before, get a wide lens, set it to f8, ISO 100 and focus the same way. But this time use a faster shutter speed. Try 3 or 5 seconds. Point your camera at the sky and fire repeatedly. With a shutter speed of 3-5 seconds you won't be getting the ambient light in the foreground, but again, it is going to depend how much light there is in your area. What you get is a photo of (hopefully) a lightning and some tree silhouettes, pretty much like your shot #3. It requires a little bit more luck than method 1, but certainly less than shooting with 1/50.