Hi Alison-
First off, I am hoping that you are looking to expand your disipline techniques and not just starting down this road...
A few things we find that work really well are to get down on your child's level and speak directly to them while making eye contact. This goes for all types of disipline measures.
1) When to Say "No" - I think "no" is an appropriate reprimand for minor infractions. We use "no" in our house for things like not touching the stereo or other breakables. We also use "no" for teasing the dog/cats or opening the patio door after we have asked her not to, etc. This is like a first level offense. Now, don't get me wrong, being first level does not mean it is a one time warning. It may take repeative action to enforce what we are saying. It also may take a distraction technique like "No, we are not playing with the stereo. That is Mommy's and Daddy's toy... Let's play with your dolly/puzzle/etc."
2) Time outs - We have found that time outs are an effective tool for boundary pushing issues like actually smacking the dog around (instead of just bothering her) or refusing to eat nicely by sitting at the table or picking up toys or for tantrums. We don't tolerate tantrums in our house, but you have to be able to distinquish what is a true tantrum versus a break-down from the inadbility to communicate yet. We use a "1, 2, 3 strikes, your out" method with warnings. If we get to 3 then it is to our naughty chair. We purchased special kiddy chairs that we keep stored away so that they are not play toys. They are only used when she is getting a time out. Time outs are typically their age plus 1 minute and she must stay seated the whole time. Afterwards, we get down on her level and we talk. She has to say sorry and tells us what she is sorry for - not listening, not picking up, not being nice - and then we get huggies. We try really hard to give her the words she is missing by saying things like "I know you were angry because we are picking up your toys, but it time for bed and we always cleanup before bed"
3) Ignoring - I have a tendency to do this more than my husband. As long as she is not going to get hurt, hurt someone else or break something, I will let a situation play out. The one catch is that since Hubby is the primary caregiver, I always ask him about the boundaries he has set for our daughter. IE. If she must sit to eat at the table, then that applies to all meals, all the time, no exceptions. Consistency is key to all of the disipline tools.
I know that is can be very hard, but you need to keep your cool as the behavior you model will be the behavior she uses to cope as she grows and gets older.
As for stress releif, I am a very physical person and getting your kids involved in some sort of exercise like walking is a huge help for me. My daughter's favorite activity is to go to the Heritage trail, park at the Monroe Park and Ride and walk the 2 miles down to the gooseponds. When we get there, I can take a break and sit on the benches while she plays on the playground. I also enjoy reading. Putting my daughter down to sleep at a consistent time (8:00pm) every night gives me a few hours (8 to 10pm) before I need to crash so I can pretty much do what I want then including getting in some "hubby time".
Best of luck!
~C.