(1) Evaluation: Are you ready to make the jump?

This step is pre-TH8 when you are in your last stages of being a TH7, the good days most would call it. You should start with an overall evaluation of your base, see what buildings you have maxed, what buildings you do not have maxed, what level your troops and barracks are and lastly, what buildings (or walls) you can upgrade during the town hall upgrading period. I wouldn't reccomend leaving yourself with more than 2-3 things to upgrade during the town hall upgrading period as you should be spending most of your time gathering and holding resources for when you first hit TH8 and need to do your big upgrades. One thing that is common and is reasonable is leaving a FEW walls to do while your town hall upgrades, no more than 15 I would say. When moving to TH8 from TH7 you want to have all of your cannons, arhcer towers, mortars, wizards, air defense and your clan castle maxed, without a doubt. The wildcard is tesla's, you want to have both of them built of course, but having them maxed out while it is helpful, is not crucial. Having maxed lvl 7 walls will also help you out, I would reccomend it to everyone.
When you have evaluated your base and it meets these standards, the jump to TH8 is awaiting you.

(2)Planning: Having your TH ready at the proper time

One step that is often overlooked (even I have overlooked this in the past) is the time you upgrade your TH to lvl 8. No I am not referreing to the day or anything, I am referring to the TIME of day. You want to have your TH ready either mid day or when you wake up, no sense in having it ready right before you go to bed or when you are asleep, as you will not be able to maximize your time and upgrade you can get done right when you hit TH8.
So making sure your TH will reach lvl 8 when you are awake and active is a very key step in making the transition to TH8 all the more successful.

(3) Initial Impact: What to do first at TH8

When you reach TH8, you should have all your storages full, the first upgrade you want to do is your laboratory so you can get the extremely powerful lvl 5 troops. Depending on how many builders you have for your village the amount of new buildings you can get will vary, but I would reccomend leaving one open so that you may build and upgrade your 50 new walls to a healthy level and actually use them to re-design your base. Here below are a list of the new things you unlock and which ones you should prioritize (defenses):
(1) Wizard Tower 
(2) Archer Tower
(3) Air Defense
(4) Tesla
(5) Walls 
You want to get all of these defenses built and to a reasonable level bfore you begin to work on maxing your existing defenses, in the words of another forum user, "Any level defense is better than no defense". ALL THESE COME AFTER THE LABORATORY.

The other things you unlock that aren't elixir related will not enhance your base too much, except the dark elixir drill, which should be prioritized above the other non-defensive upgrades.
First impact and the things you chose to upgrade when you first hit TH8 are crucial to how quickly you progress, upgrade the wrong thing and you could spend days waiting for a free builder.

(4) Troops: What to do in your laboratory

One of the most common questions when people get to TH8 is what troop they should upgrade, what troop first, what after and which ones to prioritize. This all depends on what you use most often, some peoples order of upgrading their troops might be different from yours, which may be different from someone elses. It is important to recgonize and prioritize the troops and spells that you want done first. The first troops I would reccommend for everyone is the archer, this is because they mix into any troops compoisiton just fine, will enhance any army composition, are a great troop to donate to your clan mates and a lot of clans have a lvl5 archer required to join. Here is the order I upgraded my troops and the order I would reccommend for the average player who is not quite sure of what to upgrade.
(1) Archers
(2) Giants
(3) Goblins
(4) Barbarians
(5) Wallbreakers
(6) Wizards
(7) Balloons (not very fond of them, they can always be swapped in order with the wizards however)
As for spells, prioritize upgrading your lightning and rage spells,

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