When is the best moment to do Nashor?

Yesterday I was playing a normal game, and I suggested to do Nashor.
One of my teammates said: Are you crazy? I was reading about that but I didn't get a clear answer, but I know it's a really good point for you team if you can kill it.

So i dont know if I am crazy or not, but i want to know:

When is the best minute to do Nashor at the game? (because it gains hp every minute right?)
What factors affect to do it?
It's good to use it to initiate a tf?

Baron Nashor Benefits

Baron can be very beneficial to your team. The monster drops 300 gold to your entire team and the buff gives stats equal to about 3000ish Gold per person (Depends on the gold efficiency in LoL). It is enough to turn a team that is slightly behind to being overwhelming more powerful.

With this kind of power you can force the enemy team to make a choice, push out at the peril of getting ganked, let their lanes be pushed in from all sides and try to hold it back or try for a very strong initiate and win a fight. You'll notice all of these options are insanely risky and if they back fire give you a very good chance of winning the game immediately after.

Don't underestimate the power baron can give to your team. Knowing the benefits is half of knowing when to baron because baron is not always free and you need to ask yourself, is it worth not getting a tower or something to baron.

When to Baron

You're looking to baron in general when:

• Your entire team is alive or will be alive by the time he dies.
• You have someone who can tank and survive (A character with sustain and good armor)
• You have a lot of DPS (AA champions, Cassepoiea Type AP champs, etc)
• A key member of the team who cannot get to baron quickly is clearing bottom (Do not do it if it's a shen of TF or someone with teleport)
• A key member of their team is dead (AD Carry, AP Carry, a major portion of CC, if they're alive but away and it's a carry they could clean up everyone)
• You have smite and other ways to burst him down to prevent a steal
• You have methods to pull in and kill enemy champions who try to steal
• The enemy base is being pushed in hard by super minions and if they leave they will lose significant portions of the base

Typically you'll want to engage a team fight on him if they're the ones getting attacked by him and you can get a very strong initiate. You will want to get baron if you can as well but focus on finishing them off. Nothing is worse than them getting baron and winning the fight anyway.

Baron can add more dps to your team than a tower so if you can keep the enemy team in a spot to be hit by baron all the better.

There are many more variables than can decide whether you should baron or not and it can be very difficult at times to tell when they lean in your favor or the enemies. Try to consider how the fight will go, who will be there, would they engage on you, can you prevent a steal and is it worth it over just taking more towers or ganking them.

Baron Vs Nexus

It's important to recognize when not to baron.

I see a common mistake in a lot of matches is when they win a fight in the enemy base and they take an inhib that they will leave for baron. Late in the game death is extremely long and towers can drop like flies. You can often easily win a fight at the inhib turret at mid and push all the way to nexus and kill before they will be up.

Try to consider how much dps you can do and who will be up first and how long it is between people. If it's a support coming up first they can't do squat about a full team eating the nexus. Also consider if you can just kill the one person coming up before anyone else does to increase the time you have to break the nexus.

Remember, the point of the game is to destroy the nexus, everything else is secondary. Don't be afraid to eat a few tower shots to break the nexus turrets. Also just eating those waves of minions at the nexus will cause the lanes to all push causing a build up of minions and super minions. Even if you don't get the nexus, they may be so over run, you can retreat, ward, do baron and return before they can leave their base.

Trying to do Baron before your team is around level 13 is probably a bad idea, on aggregate, because you simply don't have the damage to take him out at any kind of speed or without losing major health.

Even then, you need to know where the enemies are, or at the very least prevent them from knowing where you are. This usually means an Oracle's, but can be done in a pinch by Vision Wards. You need to know that you can fight both Baron and anyone who can get to you in time at the same time. If the enemy jungler is up, you also need to be sure that you have an ally with easy CC ready to prevent him from a sneak-steal, and your jungler should definitely have Smite available.

As far as using Baron to bait a teamfight goes, that tends to work better as a threat than as an actual attempt. You would ward the pit, and clear enemy wards as usual, and then lie in ambush near a ramp, rather than having Baron damage you himself. (He's stronger than you might think.) Only when you are much stronger can you reliably start baron, then kill an attacking team.

Perhaps most importantly, you need to make sure you don't lose more than you gain, trading Baron for bottom and mid inhibitors and towers is likely to cost you the game.