Once I solve a Rubik's Cube I obviously want to start again. I just scramble it until it seems to be enough; however, sometimes when I then solve it, I can skip entire steps from the beginner's method. Is this normal or was the cube not scrambled enough? How can one determine if the cube is scrambled enough?
Each set of moves is designed to correct a parity error in the cube's layout, but each group of parity it corrects is essentially independent and random. Each step has a chance of already having the right parity. For instance, the way I do it is solve the bottom two layers and then attack the parity errors on the top one at a time
- Make sure all the edges are right-side-up
- 3 possibilities
- Make sure the corners are in the right order
- 3 possibilities
- Make sure the corners are right-side-up
- Not exactly sure. 5?
- Make sure the edges are in the right order.
- Not quite sure either. 5?
- on a 4x4 there can be a flipped edge
- 2 possibilities
- on a 5x5 there are a couple other funny edge things
Now, the probabilities probably aren't equal for each parity state, but at each step there is a fair chance at already being in the right state. That's just how randomness works.
I'd say if you need most of the steps most of the time, you're doing fine. After all, when you practice you are really just training yourself to recognize and correct the errors. As long as you're encountering all of them once in a while, that's all that really matters.
There are lots of places for scramblers, and provide a very good scrambler, because of the fact that the scrambles can reach all 44 quintillion positions. Here are scramblers, along with timers:
Or, for an official scrambler, download TNoodle (No link, because not enough rep.)
Skipping steps (especially with the beginners method) is absolutely normal and happens all the time. As far as scrambles go, there isn't really a way to figure out a whether a hand scramble is good or not. It's best to use a scrambler (usually a part of timer software), such.as cstimer. The official WCA scrambler is called TNoodle.