This post is about the end game. I consider end game to start on your 4th turn so it could encompass up to four player turns. The game now has variable turn length so you need to plan appropriately. You also need to monitor the speed at which the game is progressing because in a tournament it's quite possible you'll only get four turns. I keep an eye on the clock if my opponent is slow. By slow I mean that my opponent takes a long time to deliberate their turns. I am opposed to rushing your opponent and to be honest I can't think of anytime that I have played anyone that is stalling. I think that some people confuse long turns played by an opponent as slow playing. Let's take Imperial Guard as an example. Typically IG armies will consist of many units and there are lots of vehicles. It takes time for the IG player to decide how they want to move and shoot as that is what they are all about. Movement is much more important in 5th edition and static gunline armies have now gone by the wayside. So IG have a lot of units to move then shoot.
I know that often I am slow when playing the first three turns as these are very important for establishing your end game. If you rush through the first three turns you will probably not create a solid end game. After the third turn I do think that the game should typically move at a faster pace since there will be less units left on the table and by then it should be clear what you need to do to win. While it's possible to win a game in the first three turns this will rarely be the case versus a good player, simply they won't let you do it as they will counter alpha strikes and huge multi charges. There are occassions when I have played opponents that also are setting themselves up to win in the end game and if their army mirrors yours it can be a lot like a chess match. What's unfortunate is when an opponent such as this takes their time and then tries to hurry you up during your turns. To me this immature and you need to brvable to effectively deal with it constructively. If you need time to properly decide how you will move, shoot and assault don't let your opponent rush you along as most likely you will make some mistakes.
So before I go into detail about end game tactics it's important to first discuss how to best setup to create the optimal end game. I have noticed that the best players are extremely adroit when it comes to movement in general. They can make it look so simple that it's easy to overlook what they are doing; the master tacticians will use their movement phases to counter your tactics and deny you the win. To me nothing is more important than your movement phases. I typically play armies that are stronger in close combat than shooting so I need to move my assault units into position to assault as much of the enemy units as possible and also be in position to maximize my assaults. Most armies have some shooting and it's also important to not overlook this aspect. A little bit of shooting can go a long way to acheiving the win. Shooting armies on the other hand are typically very weak in close combat and they will fold if you can assault enough of their army. So you want to put yourself in a position to deny them as much shooting as possible and force them to castle up so you can assault the bulk of their army. If you let your opponent spread out then when you assault and win combats your squads will too far away to quickly reach the rest of their army and they can focus fire on your isolated units; you will lose the war of attrition.
If you are playing an assault army it is possible to win the game by the third turn if you can destroy enough of their key units while keep most of theirs intact. Putting the pressure on early can force your opponent to make mistakes. Sometimes when two equal players face off against each other all it takes is one mistake to win or lose the game, especially when the two armies mirror each other. This happens quite a bit in tournaments with people choosing to play the metagame and field popular lists they see on the Internet (e.g., Lash Spam, Mech Vets, Vulkan Marines, etc.). This is one of the main reasons why I typically frown upon playing popular lists such as these... Good players will quickly learn how to counter them. If you put the time and effort into fielding a unique list one inherent advantage you'll gain is the power of being unsuspected.
So the first stage of the game is about establishing your end game and it mostly hinges on proper movement. Sure you can focus solely upon your shooting but then you are leaving yourself open. If you play a predominantly shooty list of course shooting is very important but you shouldn't focus solely upon that aspect of the game as you will be painting yourself into a corner with no way out other than to continue blasting away.
If you set yourself up for the end game then by turn 4 all the pieces of the puzzle should start falling in place and this is a great allegory for the end game. It should be obvious to you what you need to do to win by the 4th turn. An assault army should have boxed in the opponent and have numerical superiority. Often when you see two good close combat oriented armies trading blows the winner will have setup his units such that they can keep pouring more units into the combats. I have often said whoever disembarks first will probably lose, by that I simply mean that the army which receives the bulk of the assaults is at a major disadvantage as their opponent gets all the bonuses that come with charging, such as furious charge and the +1 attack. There are those armies that can absorb a lot of punishment and still dish it back out so you have to be careful when committing your units to assaults such as these. I think a big part of 5th edition is the ability to field strong and resilient units that can receive the charge from the opponent but minimize losses prior to swinging back. Units such as these are nob bikers, assault terminators and Blood Crushers. Nob bikers are the epitomy of this type unit and are extremely dangerous. You can shoot then charge them and they will still tear your head off. The best way to deal with this units is via your own movement. Try to isolate them and use as much of your army as possible to gut them. These monster units are expensive pointswise so they tend to make their armies smaller; if you can gut them then the rest of the army should crumble. Nob bikers have problems holding multiple objectives and Blood Crushers are relatively slow - again your movement is your greatest ally versus these units.
So to summarize and conclude you should be thinking ahead several turns and know what you want to do with your army. Often people say the best plans immediately fail once you roll the first dice but to be honest I think these players really don't have much of a plan in the first place. A good plan should proceed barring extremely bad luck with the dice or if you simply playing someone who is better at the game. In the latter case take your loss in stride and use it as an opportunity to learn! Don't blame the dice or declare that your opponent is cheesy... You will come away with less than nothing and face another loss the next time you find yourself in the same type of situation. Watch the clock if the game is moving at a slow pace such that it won't go beyond turn 4. There is no excuse for a game that only rescues the 3rd turn but I rarely if ever have this happen to me. If the game is moving slowly then maybe you will have to accelerate your end game, you might not get a massacre but you should still be able to win. If your opponent is slow then most likely you should be able to out-think them as they are probably to focused on simply shooting and can't link their turns together. I see this often when people come to the table with what they call an optimized list... It's only good at one thing and they are focusing on only one aspect of the game, again typically shooting. It's very easy to counter alpha strike tactics such as holding units in strategic reserve. If the mission is objective based then plan on what units of yours you want to take or contest in your opponent's deployment zone. It's very easy to play for a draw if there are only one or two objectives but not so easy to win unless you have a good plan. Playing the same list over and over will help to develop the familiarity you need to win in various sets of circumstances and to me that is a lot more powerul than simply relying upon a popular internet list.