Well, the short answer is not the night before.  (Or on your way to the wedding chapel, as one of my clients did once!)  This is not as critical for a domestic partnership agreement, although either of these should be negotiated and signed before a big event.  Thinking of buying a home together?  Have a domestic partnerhship agreement that spells out who is responsible for what.  It will help avoid conflict on down the line.  This can be a simple agreement or as complicated as necessary.  A prenuptial agreement must be done before the wedding, and a good rule of thumb is to start it around the time that you are ordering the wedding dress!  Yes, at least a few months is helpful.  I have done these a few weeks ahead of the wedding, but that is risky because I have watched people get married knowing that they compromised too much because the guests were already on their way.  Sadly, one in particularly, which I advised against, ended up in a divorce and it was hard to argue that the unbalanced consequences of the prenuption agreement should not apply because one party felt forced into the agreement. 

This is a very tough question, and there are probably as many ways to do it as there are partnership agreements.  Usually the thought of doing an agreement does not just pop into both partners' heads at the same time.  However, keep in mind why you are doing this. 

I once read an excellant blog post on this, but have not been able to find it again, so I will try to explain as best as I can what was suggested.

You both love each other and want to make sure that there is no confusion, that everything is out in the open and that you both know what the other party's intentions are.  You want to be sure that others know as well.  The best way to do that is to put it down in writing.  A component of these agreements includes disclosing everything to the other partner including each partner's present financial status.  By agreeing to disclose everything and then agreeing to figure out not only how you will conduct matters during your relationship, including who is financially responsible for what, you are taking steps that will strengthen your relationship.  You will also have provisions in case the relationship does not work out.  You want to figure out what those are while you still care for each other and are not seeking revenge.

Does that help?  Maybe, maybe not, but at least it gives you some ideas.

Of course, you need to understand that it is best to consult with a experienced lawyer to draw these up, but that you cannot both use the same lawyer.  However, one can hire the lawyer to draw up the paperwork and the other can have the lawyer review and advise for less cost.

That really depends on the facts.  It is probably worth at least talking to an attorney to determine if you need a prenuptial agreement or if you just need to take steps to protect your assets and maintain them as separate property.  I frequently end up advising clients about how to maintain an asset in order to preserve its separate property status, but there are some things, such as active income from an asset, that would be governed by statute and cannot be protected without a prenuptial agreement.  This is why an experienced divorce attorney would be helpful.  Usually an older couple contemplating marriage should have a prenuptial agreement if the intent is to protect separate assets for the benefit of others, such as your children.  These are all matters that can be evaluated better by an attorney familiar with your particular situation.

Couples who get married have a version of a domestic partnership agreement because the statutes provide for how property is divided and how children are cared for after the break up.  There are no rules for married couples about how they conduct their marriage, but if it ends, there are plenty of statutes and case law to tell us how to divide things.  Domestic partners, on the other hand, have no such rules.  One partner can contribute significantly financially, but have when the couple breaks up, or if one partner dies without a will, that contribution may not be recognized without an agreement.  With same gender couples, there can be issues that involve the children, particularly if one is the biological parent and the other is not.  The same is true for opposite gender partners if a child is conceived during the relationship.  There may have to be paternity testing and the parties may end up in juvenile court just to resolve their differences, even though things could have been resolved in the domestic partnership agreement.

Since our legal system is so slow to catch up with these situation, a domestic partnership agreement is likely the best approach to solve these problems. Again, consulting with an experienced attorney is your best bet.