Elaborations: putting others first

Let me be clear on this, I believe we should always always always put others before ourselves.  This practice is obvious and widely accepted in a few places:
Let others go through a door first (especially while you hold it for them)

After you my good man

If you've been waiting in a line and you know your needs will take a long time to be met while you know the person behind you will only take a minute (this isn't as common as it should be, but it's not rare)
Letting someone else have the last of something you want (again, not as common as it should be, but still a regular occurrence)

Hey, I'm just grabbing it to give it to you

There are others, those are just a few examples.  But, I'm talking about true sacrifice here, not just putting others wants above your wants, but putting their needs above your needs.  I'm also talking about the little things, the day to day things.

Let's say you're sitting in a room with someone and they're hot, but you're fine; if they turn on the fan, they'll be comfortable, but you'll be cold.  Someone is going to be uncomfortable, someone is going to be comfortable, I'm saying it should be you who's uncomfortable... every time.  I'm not saying it's "wrong" to mention to your friend that their comfort would mean your discomfort; I'm not saying it's "wrong" to civilly come to a middle ground.  I'm saying, wouldn't you like it if someone else let you have exactly what you want without sacrificing anything?  Then you need to provide that to other people.  Now if that other person just got up and turned the fan on, I say "Deal with it."  If they ask you ahead of time, it's up to you; you can tell them it's fine knowing full well you'll be cold, but you're not lying because them being comfortable is more important to you, it brings you more satisfaction, than you not being cold.  Or you could speak up and mention you'd be cold and the two of you can come to an agreement.

Now let's say you're on the other side of the couch; let's say you're the one who's hot and the other person seems perfectly comfortable and isn't changing anything themselves.  It's a delicate balance, and one you must approach on a case-by-case basis, part of the equation being how well you know the other person, part of the equation being how truly uncomfortable are you.  DEFINITELY do not just turn the fan on without asking first, even if it's in your own house.  But, should you ask or should you just "deal with it"?  As I said, there's nothing wrong with asking, but I think it takes a bigger person, a more mature person, a more caring person to deal with it.

Or, let's say you just finished a T-ball game and someone brought a cooler of drinks for all of you to enjoy.  This cooler contains all kinds of drinks; various flavors of soda, bottles of water, various flavors of juice, etc.  I want you to be the last person to get a drink, unless there's someone else doing the same thing.  Now, that might mean that you don't get exactly what you want, but if that's true, then that means someone is not going to get exactly what they want, so it should be you.  Why?  Because you want to get what you want, so you need to extend that sentiment to other people, and the way to ensure that is to be sure that everyone else gets what they want before you do.  Of course, if there's only one of something, then everyone is going to get the same thing; and if you're sure there's enough for everyone, then it doesn't matter if you're first or last.

The hard part is doing this sort of thing in the face of someone who's a jerk, to put someone's wants above yours, even though they've always been selfish.

Now, this isn't to say you're spineless.  This is a conscious choice you make, this is you realizing that you get more enjoyment out of knowing someone is 100% getting their way than the amount of joy you'd get if you came to a mutual agreement.  This is you doing your best to NOT be the source of any negativity.