An elaboration to this most elegant post, and how it specifically relates to LoL:
1. One of the more general maxims. I would translate this as "don't force things", or, more specifically, don't get greedy.
2+6. These two are part of the same idea. One of the hardest challenges that face new players in LoL is the sheer number of abilities and items that can affect any battle. It is critical that you are aware of these. Know your opponent's hero like your own. Know their inventory. Know their current mana pool. Know their summoner spells. Be prepared to deal with your early gank failing when the opposing hero pops his heal or drops his rally. Don't go "wtf" when that 100 HP veigar turns around, stuns, and drops 3 nukes on you that do well over 1500 damage. Once you know which heroes have stuns and snares, how they work, how much mana they cost, and what kind of range they have, the game becomes so much more ordered and strategic. Familiarizing yourself with all the details of a game like LoL or DotA (especially the latter) can take a significant amount of time (which is why the learning curve is so steep), but at least a basic knowledge of the enemy's heroes is vital to avoid feeding and eventually succeeding.
3. Mind games. Use them. Against more skilled players (particularly those who heed #s 1 and 2), deception loses power. But if you're that 100 HP veigar running away from an eager hero looking for a kill, you might be able to get him to pursue further if you wait to pop your heal until the last second. The enticement of the kill is what draws him deeper into your territory. Maybe after he tanks a tower hit or two, you can nuke him down for an easy kill.
4. Listen to your teammates and heed their mias. Good communication is key for things like timing stuns, executing ganks, etc.
5. You could link #5 to things like backdooring or pushing to avoid confronting a more powerful foe, but in a fighting game, #5 doesn't make a whole lot of sense.
7. Don't dally! If there's an opportunity to end the game, or a temporary advantage that can be exploited, then by all means exploit it! Capitalize on the fact that your early gank forced the enemy lane to blow their flash/heal in the first minutes. Play aggressively and either deny them farm or force them to take damage (or death) if they get close to the creeps.
8. Probably the most important rule, depending on the kind of person you are. E-peen stroking is a big part of every competitive online game, but let's say you want to show off and you, as Jax, leap into the middle of 5 enemy heroes. You kill 2-3 before being gunned down as you attempt to make a getaway. Now, this secures you epic bragging rights (depending, of course, on the relative skill level of the enemy heroes), but wait! Turns out, you were the only worthwhile player on your team, and with you gone, the remaining enemy heroes push down an inhibitor. Sad day!

Disclaimer: I enjoy e-peen stroking. I would completely disregard #8 in anything but a "serious" match.

A lot of good points all over.

I'd say for me, the most important thing in late game is what everyone said, try and stick near your team and find targets of opportunity. If you can snipe 1-2 heroes then you're almost insured taking a tower/successful push.

As far as cataclysmic 4v4's etc go, well, I'm not sure just how much you know about the game but to do what you're saying requires a lot of knowledge. To be able to tactically know what to do really is nothing more than knowing what your heroes are capable of and what their heroes are capable of. Do you have 4 stun/bursters(heavy nukers) to their 3 carries? Charge in if they come out of safety range of the towers and try and JUMP one of them since you can nuke the **** out of a single target and get a carry. Do they have a fragile caster/disable like fiddlesticks? Try focusing on him if the battle merges and disable/kill him before he can get his Fear/AOE ult off. These are not always easy to if he DOES cast his stuff, usually teams either bail out of the aoe of his ult to not die, or switch to other targets, etc. Either way, definitely try and concentrate on knowing who can kill you the hardest, and think about what your team can do about it (hopefully take him out first in every fight so you can have a cleanup on the rest of the team, but that's not always easy).

I guess my main point in summary is to know your target priorities and roles, and that can only come with time and learning pretty much every hero and what they can do. This takes awhile. After that knowing what to do tactically in a battle is much easier. Tanks charge in to draw fire/stun for initiation, casters tend to stay back and sling spells, and carries like to come in last after the enemy team has blown all their nukes to clean up on everyone. These aren't the "pro" strats to follow for life, but definitely how you could expect an average game to go with average players. Hope this helps, and keep on truckin, learn those heroes and it'll all fall into place better!

Veigar is a fantastic anti-blob character with his Dark Matter and Event Horizon abilities.

• The late game is all about making correct decisions, situational awareness, and knowing the map as well.
  
• Seeing a solo enemy champion could either be an easy kill or a clever ruse to draw you into a gank trap.
  
• if enemies are missing they might be killing the dragon or the baron, or they might be getting into a position to gank you or your teammates.
  
• if even one or two enemies dies it is a good time to group up as a team and push a lane, possibly try to take out an inhibitor.
  
• depending on your hero of choice, some heroes are better to initiate large fights and others are better when they come in partway through the fight. As an example, my favorite hero is fiddlesticks. I typically try not to be in the front of the battle or even be seen in the beginning so that I can wind up my ult and run in from the side or from behind and lay down massive AOE dmg without instantly getting CC'd or killed.
  
  On the other hand, if I'm playing Cho'Gath I always try to initiate fights and open with my AOE stun, silence, etc hoping to get enemies to focus on me rather than my teammates.
  
• If there isn't much action on the map at the moment you might be better off jungling for a bit and getting some money, neutral creep buffs, etc.
  
• oftentimes running can be a very effective strategy. If people see that you are low they will tend to chase or if you annoy them or damage them enough they might also chase out of spite. If you are good with your hero and have a good knowledge of the map then you should be able to keep them at bay long enough to lure them into a trap. I can't even count how many times with fiddlesticks I have gotten kills by running, waiting for cooldowns, and then turning around and melting people before they even have a chance to do anything in response. Or possibly leading them into my teammates who came to help.
  
  These are just some general tips I can think of off the top of my head. I hope some it was useful.