I'm a time-outerer. Up to Age 2, my daughter was more frequently misbehaving - and parents need to understand that this is natural. Age 2 (the "Terrible Twos") is when a child is trying to establish what his/her parents' boundaries are. The only way they know is by testing his/her parents' limits. And IMHO this is the most critical time to be really firm but fair when it comes to discipline -- because if you can get your child to be self-disciplined before age 3, then things get so much easier! We were constantly verbally reprimanding and time-outing Yuki from age 1-2. And yes, I would time her out in public. I once established a Naughty Corner at Kansai International Airport in Osaka Japan while lining up to have our passports inspected; I made her stand in that corner for about 3 minutes until she settled, then I squatted down to her eye level and verbally counselled here before moving on.

But when it comes to discipline, I believe in 3 core principles:
1. Be firm.
2. Be fair. Don't be too lenient nor excessively punitive. Also, try to be emotionally detached; always criticise the behaviour and never the child's personality (e.g. don't say, "You're being an idiot!" but rather "That was unacceptable!"). Also don't forget to reward good behaviour; the other side of the discipline coin is positive reinforcement when they do things right. Just simple things like verbal praise, hugs, kisses etc. (e.g. "You've packed away all your books, aren't you a good boy/girl!" <hugs><kisses>)
3. Be consistent. Any time the child steps out of line, issue a consequence (punishment). Any time the child does something good, issue a consquence (reward).

By about age 2.5, my daughter had quickly learnt that there is a 100% chance that there will be a consequence for any of her actions -- both positive and negative reinforcers. Since age 3 we rarely have behaviour issues with her. I've never had any of her teachers ever complain to me about her behaviour; they all say that she's excellently behaved. Her Chinese school teacher told me that although she is physically the youngest child in the class, she is the most emotionally mature - that was last year when she was still in Kindy, and all her other classmates were year 1-2 or older.