Take objectives. That's about it. Honestly, people need to learn to recognize their comp and what they are good at.
I had a game as Miss Fortune where we were getting destroyed. I kept telling our Tryndamere to splitpush while we defend. Instead, we kept trying to team fight. The enemy team even remarked in the end game chat that we couldn't win a 5v5.
I had another game as Nasus where my team kept getting caught out or team fighting when I wasn't around. It would be a 4v5 and instead of teleporting in, I would take a tower. I ended up getting an inhib for free while they tried to siege our base because they wouldn't tank the nexus towers and instead waited for minions. We aced them soon after and ran up that lane to win.
I just had a game as Miss Fortuen where the enemy team was 4 tanks (Rammus, Tahm Kench, Alitstar, tank Akali, and Ezreal). We had a Yasuo, Azir, Fiora, Thresh, and MF. They took two inhibs and then let us fend off waves forever. We finally got a few of them in a team fight and got baron. With that, we were able to almost ace them again and won off straight pushing up mid with our baron minions even though I think we still had two inhibs down. Honestly, I think they could've just walked into our base, tanked our 1 nexus tower and our damage, and ended it if they thought about it but they never did. Even when I ulted all of them, it wasn't straight out killing anyone aside from Ezreal. I mostly used it for the black cleaver shred. We stalled long enough for me to get a Bork and Lord Dominik's.
http://matchhistory.na.leagueoflegends.com/en/#match-details/NA1/2204444659/230464500
If you Ace the enemy team, get whatever you can get safely. This is my general guidelines, so they may not be completely accurate and depends on each game, but it works for the most part.
Nexus > nexus tower > inhib > inhib tower > baron > inner tower > outer tower > dragon
Obviously there are issues with it, but it's a good rule of thumb. If you ace them in your base, you may be better off getting baron/dragon instead of trying to push through the minion waves to get a tower unless you have good wave clear or can split to take both at once. Same that if you ace them bot, getting the bot outer would be better than getting the mid inner because you are already there and have easy access to dragon after getting the tower.