This is not legal advice. This is crappy internet advice from people you've never met. But it's also advice from someone who is married, who has family we don't completely trust, and who has been involved in the fight for equal marriage rights for nearly 15 years.
There are a couple of things to be concerned about as a gay couple, married/DP'd,/CU'd or not:
1. Family
2. The Government (includes all bureaucrats and organizations like hospitals, nursing homes, courts, etc)
1. Do everything you can to make your relationship codified and known to everyone. This means getting all available legal protections -- DP, marriage, commitment ceremonies, etc (some of these or maybe all of them) -- even if they're not honored in your state, or even if they're not legally binding (eg, marriages by a UU or UCC church are valid marriages in the eyes of those churches, but not necessarily the state). It means power of attorney. It means end of life directives and possibly living wills. It means having the frank and hard discussions with your partner and friends.
2. TELL EVERYONE that you're a couple. This means being out. Why? Because if you're dead and your partner is incapacitated, you will need to rely upon the kindness of strangers to honor your wishes, or if you're battling an idiot hospital nurse who thinks he's God's security guard and that keeping the homos apart will get him closer to heaven. Tell people that you've got your partner's power of attorney. Use words with the people who have some control over your lives (your doctor is the best example I have) that indicate you're a couple: my husband and I, my partner and I, we, the two of us, etc, on a regular basis so they aren't surprised when it's suddenly important and act not out of spite but out of ignorance.
3. Travel with your legal documents (not your wills) that indicate you're a couple that a hospital might require to ensure your right to make medical decisions on your partner's behalf. And by travel with, I mean the glove compartment of your car, not just on vacation. I don't necessarily mean on the bus or subway, but it's a good idea to keep a copy at the office too. Where are you most likely to get injured? Probably your car. Consider some sort of wallet-sized version too.
4. Make sure a 3rd party -- friend, lawyer, trusted family member -- knows your wishes and relationship and can be reached fairly easily. Have a backup or two, too. If you're both injured, someone needs to be able to speak for you. Think "porn buddy" but without the upside (http://www.youtube.com/watch?v=h9gnexnnIDc and there's a missing final line: Jeff: That's the beauty of it, you see? Your best friend's dead, but there's a bright side!).
5. Make sure your wills and other docs are tight enough that family members cannot override them easily: explicitly deny them access or authority; clearly specify what they are to receive, rather than just having them next in line after your partner: And sis gets only my EasyBake oven and only in the event [my partner] predeceases me; ensure that your burial directives are explicit.
6. Have something in writing that discusses who owns what property: the stuff you each brought to the relationship and the stuff you acquired after you were a couple. Personally, I think that stuff you got after you were together should be jointly owned, but that's me. This is less important for junk than it is for stuff of value: cars, art, furniture, property, etc. And it's especially important if for some reason it's not titled in both names (thinking cars and property here, which might be in one person's name for tax or other reasons).
7. Title real property in ways that minimize the tax burden upon transfer. This is especially true when one partner pays more of the mortgage than the other.
8. Figure out how you're going to handle your money. Everything separate? Everything joint? A mix? This isn't really a protection issue, but it is a relationship issue and one that people need to discuss. We have friends who keep nearly everything separate and who say at restaurants, okay, I owe you $20 for last time, and we have other friends who put both incomes into a joint account and everything is paid from there. DISCUSS THIS so it's not an issue later. Also, the joint account is a great way to document that items were purchased together.
9. Do all these things BEFORE you need them.
10. FIGHT for your rights when you're concerned about them. Do not allow yourself to be denied access to your partner. Any hospital employee who tries to keep me away from my husband will have to have me arrested because that's what it will take. Don't let some pissant deny your last moments together. And also remember that, as I mentioned above, sometimes people will treat you inappropriately not out of malice but because they don't realize you're together. Give them the benefit of the doubt and a chance to correct a mistake (or to prevent one from happening) before going nuclear on them. But go nuclear if you need to. Also, self-confidence is key: remember that you're in the right and assume that they WILL honor your relationship. Going through customs, my husband and I have always filled out one family declaration form and never had a problem (we've only done it a few times, in 2001 from Europe, maybe 2002/2003 from Canada, and again in 2010 from Europe). We don't ASK if we can fill out one form, we just do it. Hand it to the Customs guy, answer his questions, and proceed.
11. Use common sense: if you're traveling in Iran, don't tell the hospital he's your spouse. This might be useful in part of the USA, too, or anywhere you are concerned about mistreatment if someone knows you're gay, such as a hospital when things are going fine but Nurse Ratched is your caregiver. My husband and I look enough alike (same race, close in age and builds, etc) that we can pass for brothers if we had to, and we're willing to say that if it's a matter of self-preservation. Uncle/nephew, brother-in-law, cousin, can also work, especially if they're limiting visiting hours to their definition of "family". I don't think we've ever actively used this technique, but it's in the arsenal.
I hope this helps.