First, don't be put off, I'm not going to come across as arrogant, pretending to know all the answers (at least I hope I won't!). What I can promise you though is that everything I'm going to include is going to have been learned the hard way.
First, a bit of background. I first started off in this hobby over 20 years ago at the tender impressionable age of 14. I'd previously put together and painted many airfix kits, but once painted like many I suspect, all interaction with them was limited to hanging them from my bedroom ceiling and hoping they didn't crash land on me in the night.
That changed when I discovered Warhammer though, and I started a skaven army. That love quickly spread when I read about the second war for Armageddon and I began collecting blood angels. Without going into too much detail, my gaming life stagnated once I left uni and moved back home - I live in a very rural area with no FLGS and an hour drive to the nearest GW, no one I knew played anymore.
Still, I kept reading white dwarf and painting models, which in my naïveté I thought meant I knew what I was talking about. Autumn 2012 arrived and I found a club only 20mins away, so I packed up my cobra guard marines and trundled down to play. My first game ended with me having only 3 models left on the table. A four month losing streak finally ended and I've gradually improved since then, to the point now where I can comfortably say I win the majority of my games, so that's where these articles will come from, I've been in that losing streak and mentality, and these are the things that helped me improve.
My first piece of advice therefore, and the focus of this post is about knowing your list. Sounds really basic, right? Well it is, but you'd be surprised how many people I've come across who come to a game and don't know their list. I don't just mean what units you have in it either, though it's not unheard of for an opponent to forget a model was included and never take it out of their bag. When I say know your list, what I really mean is understand your list - why have you taken the units you've included and what are they intending to achieve in any particular game.
I mentioned that I had a four month losing streak when I got back into the game - there were some fundamental reasons behind that, and understanding army selection and unit selection was what cured it.
So how do you go about understanding your list then? There are three key points:
1. You need to understand the fundamental rules of the game and how they apply on the tabletop - recognising that the current edition of the rules places shooting in a stronger position than assault was a key thing for me, and also understanding how the cover mechanic worked (I've played plenty of games against guard who would simply duck behind their aegis line and get a 2+ save, then stand straight back up and fire normally in the next turn).
2. Second is understanding your own codex and it's strengths and weaknesses, and both veteran players and internet reviews can be hugely helpful in this regard.
3. Third, and the most relevant is understanding what each unit is capable of.
I don't want to go into too much detail on the first point, I'd expect new players to make sure they learned the rules properly and to read around the subject to understand them - there are often subtle nuances to the wording that you don't get first time round.
The second point is where this article really kicks in. Understanding the strengths and weaknesses of the codex is crucial to both list building and in game tactics. When I went back to basics with my model collection with a view to revamping it for 6th edition, the first thing I did was to go through the entire book, listing whether a unit was intended for anti tank, anti infantry, anti air or anti elite infantry. This included looking at weapon upgrades and alternative loadouts so sometimes a unit would have more than one entry in my list. I then looked at the strengths of each individual unit and more importantly their weaknesses so I truly understood what everything brought to the table.
So the final point then, when writing the list, I combined all these factors to give me a competitive finished article. Here's the thinking:
What wins games? Objectives. So you need units that are capable of both holding them, and claiming them, and that needs different attributes. Holding objectives in your own half requires resilience, either from innate toughness, good armour or ability to utilise cover to it's greatest extent, and it also requires that those units can affect the game from those long distances. In my marine list, this tends to come from my centurion unit, armed with lascannons and missile launchers. They're tough, good save and long ranged. Their weaknesses are that they have no invulnerable save, and they can't fire overwatch, plus they really don't want to be in combat with much. By understanding those weaknesses I can plan for them, providing my centurions with a backup squad who can lay down some serious hurt on anything that does approach my lines with combat in mind.
So that's home objectives taken care of, what about others? Well in terms of claiming them, troops units are best, since they get objective secured, and being fast enough to claim them early, or appear to not threaten them is key, so in came two bike squads and a bike mounted captain to make them troops. Bikes biggest weakness is their cost, though there's little you can do to ameliorate that besides taking cheaper units to fill out the roster or accepting that you'll be outnumbered.
I'm not going to go through my whole lists but hopefully you've got the idea, by understanding the strengths and weaknesses of each individual unit you can have realistic expectations of what they'll achieve for you on the tabletop, and you can also identify what tasks they can achieve that you may not have planned for.
So there you go. Understanding your list and why you take each unit is the first step on my path to becoming a better player.