I've constructed myself numerous lists throughout my time playing 40k and I've shared a few of those with you folks of the community, but honestly I've even thought about the process I go through to design a roster. I realize that many of you are probably professionals at this, but I thought I'd at least give you insight into why/how I make these rosters and explain how I come up with some really wacky lists.

Primary Focus

Every time I start a new army roster, I come up with a primary focus which is something I've really wanted to try out or something that's really cool and I want to try out. For example the roster from my "Raining Suits" list, the focus was deepstriking suits galore.

The primary focus should be the fundamental part of your roster, the main strategy or tactic and it shouldn't be just one unit, but it should involve a majority of them. In the "Gunline" list that I posted, the primary focus was a gunline and it involved a Riptide, three squads of Fire Warriors, a Sniper drone team, an Ethereal and two squads of Pathfinders. In my "Ripe with Dirty tricks" list, I focused on outflanking my units via the Positional Relay for reliable ambushes. This involved a squad of Kroot, a Riptide, a squad of Pathfinders and a Broadside.


In all of the examples I provided, about half (maybe a little less or more) were involved in an army wide strategy which was my primary focus and I always start with this first.


The Core

The second most important part of any army is your core. Every person has a completely different one, but this is what you can't leave out of any roster you play. For me this would be at least two squads of Fire Warriors, at least on squad of Suits, a Shas'o decked out for heavy combat with a bodyguard squad, at least one squad of Pathfinders and at least two heavy tanks with one of them always being a Railgun toting Hammerhead.

 
This is what I would call my core, because I always put this into every army I write, no matter what my primary focus is. That's why you'll see a lot of my lists just look like reworks of each other, because I never leave my core behind.

Edit your Core

Now that you know what your core is and what your primary focus is, toss in the core of your army and then modify it until you feel it plays along with your Primary Focus (if it doesn't then just do your typical core loadouts).

Once you've done this, add in whatever units you need to complete your Primary Focus.

Covering your Bases

Next, check your army list to make sure you have all of your "bases" covered (anti-air, anti-armor, anti-MEQ, anti-horde, etc.).

If you don't feel comfortable that you've done this, then you can add in some more units to compensate or modify the ones you have.

For example; in my "Gunline" list, I didn't feel that my gunline could deal with MEQ much, so I added Rail rifles into my Pathfinder squads. In my "Raining Suits" list, I didn't feel like I had enough anti-armor, so I edited my fusion bomb suit squad with a Support Shas'o to make them extra reliable at blowing up tanks.

 

Funny Bunnies

This should always be your last part to your list, but probably the funnier part. This is when you just add in stuff that you'd think would be fun to play with or just to try it out.

In a few of my lists, I toss in Piranhas for anti-armor, although they're not my most reliable option, I still like to use them because I love the models and I love going "Vroom, vroom!" I move them across the board (Yes, I have on several accounts made that sound while moving my Piranhas across the table).

In some of my lists, I'll add in a crap ton of drones just because I can. I'll give my Broadside two missile drones and a target lock just because. At the same time I'll give my Riptide two shielded missile drones and a target lock, just because I can and I have the points.

Sometimes, you can even turn this into a secondary focus if you really wanted to. Just to have a back up plan, if your primary focus falls through (DARN you unreliable reserve rolls!)





That just about covers my thought process while I'm making my lists. I hope this helps those of you out there who may still struggle with this and I hope you veterans out there found some good pieces of advice or at least had a good laugh.