First Things First!
Some things to think about up front.
There are a lot of things you need to put in order before you start. If your really going to go through with the divorce then you should make a list and evaluate it and what your "ready to do".
What I mean is this; are you emotionally ready for a fight? Are you financially ready? etc.,
Financially Speaking
Are you going to hire an attorney? If so you need to figure out your budget unless you have enough in the bank that you don't need to worry. Attorney fees vary wildly from my experience. Some attorneys work on a sliding scale based on your income, even so expect to pay at least $175 an hour and upwards of $450 an hour. Some attorneys with "big" reputations can go as high as $750 an hour!
Don't stress out yet many attorneys will set up a payment plan so you can hire them. Most will ask for a retainer upfront, again this varies but I have seen $2500 as an average. One thing you can do is get as much of the work done your self as you can and only go to the attorney for questions, you'll still have to pay but you'll spend less. Also not all attorneys are willing to work as a mentor for you.
Some attorneys will allow you to do the foot work though. You can hire them and when things like court papers need to be filed or delivered you can handle that. It will save you some money but not allot. If you're going to have simple divorce with no disputes then you can get a paralegal or an attorney in training to tell you whatforms to fill out and how to file. As well as setting up some basic agreements between you and the ex.
Court fees vary but expect to spend between $50 and $300 to file all the forms. Serving papers can also cost you. You may be able to have a friend serve for you but if not you will need to hire a process server to serve you court papers, even if the divorce is amicable. It's the law, and you have to have proof of service.
Child support is something else you need to think about. You or your ex may have to pay support unless you decide not too and just split expenses. My advice fro both side would be to do your best to keep the "system" out of your personal lives. Keep as many decisions out of the courts as you can. Once you let them in there's no going back. And believe me their system sucks.
Emotionally Speaking
Are you ready for the fight? Are you ready to be separated from your children for days or even weeks at a time? Whether you like it or not yor going to have to share custody of your children unless your soon to be ex has serious problems that you can prove.
Also are your kids ready? You may think you are ready but how about your children. Your children undoubtedly love the other parent unless he/she is really a bad one.
So I need get on a soapbox for a minute here...
I have seen many friends split up over the years some have had really good reasons and some have not. Good reason are things like, abuse, alcoholism (maybe) drug addiction (maybe), cheating (maybe). But if you just need to "find yourself" or you got married to young and you need "some time to explore" then your an idiot. Too strong for you? Too bad, I've had friends split becuase one or the other felt like they "needed to grow", it was devistating to thier children.
Kids need a stable enviornment with their mom and dad in the same house, not your new boyfriend or girlfreind. No one can replace either of you in thier minds or hearts. If you have been cheating and you have so delusion that you and your new love afre going to run off he/she will be the new parent to your kids the your a double idiot. You are going to hurt your children to no end with a selfish manuver like that.
Ok off the soapbox...
If your really going to go through with it the you should talk (if you can) with your ex and come up with the best plan possible. Talk toa professionl, a therapists, about the best way forward to minimize damage to the kids. Get a plan in place and stick to it. No matter what you do your going to hurt your children and you need to be prepared to watch for signs that they are in distress. Talk to thier teachers and let them know what is going on so they can keep an eye out for sign that the children are in need of help. If there is alott of fighting then find a child therapists now so you can get the kids talking to someone right away. If it seems like I'm spending alott of time on the kids that's because I dont care about you, you made a stupid mistake and now other human beings that have no say in the matter have to pay for it. Sorry the truth hurts.