I think discipline starts from the beginning when they decide to bite you on the boob! I take Jesse off, say no & he doesn't get it back.
When they start crawling you discipline them to get them away from power points etc.
My girls are older, but I find they get it better when I explain it to them. Eg, feet on the table is rude, rather than just no. But at her age you aren't going to get too far.
Just keep persisting gently.