Step one: get informed. Find out all you can about separation and divorce. The
Federal Justice Department web site is a good place to start. Especially if you have children: read the Federal Guidelines for Child Support!!! You can also get lots of information directly at the court house (flyers, booklets, etc) and you may even be able to speak to someone about what you need to do.
Second step: go to a mediator. A good mediator will walk you through the process in a logical and (hopefully) unbiased manner. Remember, they have seen many situations and you would be surprised at some of the innovative solutions they can propose for even the most sticky problems.
Third step: pay a couple of hundred dollars and hire your own lawyer to review the agreement produced with the help of the mediator BEFORE you sign it. A good mediator will insist on this. If adjustments are required on either side, go back to the mediator to sort them out.
Finally, some mediators will even file the papers for the agreement and take care of the divorce application. You may not even have to appear in court. Moreover, the cost is shared, and in some jurisdictions (notably in Quebec) even subsidized by the government.
As for details, I would suggest trying to stay as "generic" as possible. Eg, make child support to be "in accordance with the Federal Guidelines for Child Support", with a commitment for disclosing income on a yearly basis. That way, adjustments can be made as you go.
AND ALWAYS KEEP IN MIND: court is and always should be a LAST RESORT. It is for when there is absolutely no way the two parties can reach an agreement. If either party is unwilling to parlay with the other, there may be no choice but to have "some perfect stranger" (a judge) make decisions for you both (never a good thing!). And remember this: A lawyer once told me that even a bad settlement can be better than a ruling!
Good luck. I hope reason and logic will prevail in your current predicament.