Ok, so I promised some folks that I post some images of my healing setup and instructions on how I configured it, so here it is.
Before I get started, this is the list of grid-related addons I use:
Grid - The base addon.
GridDynamicLayout - Sorts raid members into dynamic groups. I'll explain more later.
GridIndicatorText3 - Adds a 3rd row of text to each grid box.
GridStatusHots - Adds indicators for HoTs showing the remaining duration.
GridStatusLifebloom - A textual indicator for lifebloom showing number of stacks and remaining duration.
GridStatusMissingBuffs - Shows raid members who are missing particular buffs.
Now, that said, here's an example of how my grid layout looks in a typical NAXX25 run:
This is using the dynamic layout addon to sort the members of the raid into columns. In this example you can see that column 1 is made up of the current tanks, columns 2 & 3 are healers, 4 & 5 are ranged DPS and 6 is melee DPS. The dynamic layout addon watches each raid members status, including stances, talents, etc and dynamically sorts them into the appropriate groups. If someone changes stances (ie. shifting from cat form into bear form), it will move them to the appropriate column(s) as appropriate.
Now let's talk about what each item in the grid means.
Take a look at Krindle's box. The number on the bottom line shows that at current, Krindle is down 3.9k health. I don't show the max health because, well, I don't really care.
The number in the middle of Krindle's box (3-4.0) shows that Krindle has 3 lifeblooms active on him with 4.0 seconds until they expire. I only show my own lifeblooms, as it would be too much information to try to keep track of everyone's.
Now take a look at Knightly's box. The green box in the top left corner shows that he has a regrowth HoT currently active. As regrowth winds down, it begins to turn darker shades of green until it disappears altogether once it's run out.
Baylie, Eppy, Dein, Jut and Zero all have a grey box in the bottom right corner. This indicates that each has an active Wild Growth HoT on them. The boxes for WG start out pure white, and get dimmer as they expire, so in this case, they're about to run out.
Zero also has a pink box in the bottom left corner. This indicates that he has an active rejuvenation HoT on him.
I use the top right corner for 2 different things. When in combat, it shows people who have an abolish poison spell active on them, as in this example:
when out of combat, however, it shows people who are missing a mark of the wild or gift of the wild buff, as I am in this example:
There are a couple of status notifications not visible in the examples. The border of a persons box will turn green if that person is poisoned, or pink if they are cursed.
It probably sounds complex, but in reality it's very easy.
Now to be honest, I'm a bit lazy. I was planning on writing out all the instructions on how to setup Grid to work properly, but there's already a very good write-up available if you're interested.
What I decided to do instead was to share my grid configuration file, so if you're a resto druid, you can copy it and go. If you're a different class, well, you can always use my config as a starting point and modify it as needed. In order to use my file, first make sure that you have downloaded and installed all the addons above. Once that's done, download my grid.lua and place it in your World of Warcraft\WTF\Account\YourAccountName\SavedVariables folder. Start up WoW, join a raid, and it should all be ready to go.
There's really so much more detail I could go into, but this should give you a start if you're looking to get into grid.
Any questions I can answer?