This section is real simple: Baron Nashor doesn't exist in solo queue. Baron, and the Exalted with Baron Nashor buff granted by defeating him, is designed to provide a strategic incentive to skirmish in the mid-late game. Specifically, having the buff allows you to push objectives and dive turrets effectively when coordinated well. That last part is important.
When used by a team that can coordinate turret aggro, maintain their formation, and focus down squishy backline targets while allowing the marksman to whittle down the tanks and utility roles, the purple buff is really strong. Realistically, the solo queue team you're on does not have that level of sophistication. At Diamond or Challenger levels, you may have the game sense to organically orchestrate that kind of play, provided everyone has bought into their role and is equally adept at performing it.
With that in mind, contesting the Baron buff in solo queue is almost never worth it. If you've built any sort of item or experience advantage, it is definitely not worth, as a semi-coordinated five-man push is going to secure at least two turrets if not an inhibitor past the 25 minute mark. You will also normally have the opportunity to grab dragon and purloin buffs from the enemy jungle.
The exception to the rule: There are actually two. You should always encourage your team to grab every free Baron you have served up to you. That's a no-brainer enough I almost didn't include it. But I'm specifically referring to clean aces, or four-for-ones or other incredibly favorable trades that result in you having smite and the carries needed to burst down His Majesty Highness, the Baron of the Rift. A two-for-two where you "know they went b" is not the situation I'm referring to.
The other is when, serendipitously, your whole team happens to be around Baron, at full health, when you catch them with their Armor/MR shredded and health bars half-missing, still attempting to slay the royal wurm. If you can't push towers and secure inhibs, because you all happen to be on top of the enemy WHEN THEY START BARON, then you're good to go in with that Crowstorm, that Unstoppable Force, that Assault and Battery.
But read that last part again. If, WHEN THEY START BARON, one of you is botlane or getting blue buff, or farming away at those Mini Golems, then you all converge wherever they are and grab as many turrets as you can. Period. Especially if you have an item or experience lead.
Baron TL;DR: Don't bother with the beast in his pit. Take turrets and inhibitors instead. Most solo queue teams can't coordinate effectively enough with the Baron buff, and it's more likely that they'll throw than succeed with it so long as your team is prepared for the siege.