This article is not going to be a complete Imperial guard tactics article but rather an introduction into how I play my Imperial guard army. With Doctrines you are limited by your imagination when playing guard.
In my previous 411th Royal Cadian Regiment (411th RCR) post I gave the doctrines I use but I will list them again. They are: Iron Discipline, Sharp Shooters, Orgyns, Enginseers and Close Order drill, now here's why.
Iron discipline gives you the ability to rally even when under half strength and it ignores the -1 for being under half strength. Couple this with a trade mark item or a battle standard (ie a re-roll for leadership) and you have a 12" radius of troops that you can rely on.
Sharp Shooters lets you re-roll any 1's to hit with the exception of plasma weapons. I know most people don't like to play mathhammer but it increases you chance of hitting from 50% to almost 60% (58% or so I think). So to me it is a simple choice.
Orgyns rock! In the current edition of the guard codex lets you have units of 10 of them. That's 30 wounds and 31 x Str 6 attacks on the charge. Not bad for a unit that costs the same as 5 terminators.
Enginseer are a totally unsung hero of the guard. Everyone likes to talk about the tanks, but you need someone to keep them in top fighting condition. That's where the Enginseer comes in, with the blessing of the machine spirit he gets a 6+ chance of repairing any damage to your vehicles. Couple that with up to four technical servitors (who each give a +1) and you are repairing anything on a 2+! To add to this he does the repairs at the beginning of the movement phase so once he's repaired something it is free to move and fight and so is he. Finally he comes with a power weapon and fist so anyone foolish enough to try and take him out has to kill all 4 servitors first and then deal with his deadly strikes.
Close Order Drill is my on again off again final doctrine. It has potential to give you the increased In and Ld when in formation but it also makes you very vulnerable to template weapons. I normally take up the formation just before charging or when I am going to be charged the next turn. But it is also the first doctrine I drop when I want to add something special, like Storm Troopers, to the 411th RCR.
When it comes to setting up I have found the best strategy is one of an ink blot. Start with everyone close together and move out from there. This limits your enemies ability to flank your force (as you don't really have a flank) and allows you to adjust movement and fire lanes to stay supporting. I use my Infantry squad to act as a fire base in whatever cover I can find. 25+ Guardsmen with medics, heavy and special weapons can be hard to route out of almost any cover.
I'm a big fan of lascannons and I like them in my squads where they can take 9 wounds before they are out of commission. Their job is to kill the enemies tanks or other big nasties. I will use my Armoured fist squad to either support the platoon or to try and stanch objective/table quarters.
Tanks are what give the guard their punch and I take 3 in almost all my armies. A basilisk for long range indirect (remember to protect it with something, I sometimes use the armoured fist squad for this) Leman Russ for long range direct fire and a Demolisher for devastating close fire power. The Demolisher normally leads the attack with my Enginseer standing behind it, both using it for cover and ready to make battlefield repairs. The Russ is my lone wolf and will look for places on the table to exploit its range against lascannon armed other vehicles and troops.
Assaulting force, I know what your thinking the guard don't assault but mine do. The Orgyns follow the Demolisher and enginseer forward with the overall command squad right behind to ensure the Orgyns don't run away and to act as a second wave.
Fast Attack is done by the Hellhound and a lascannon armed sentinel. The Hellhound is feared by anyone who understands how much devastation it can cause, 24" and arrange the template as you like with Str 6 AP 4. Kiss everything but marines, or marine like saves good bye. The sentinel forces people to kill it because a moving lascannon is enough to make everyone a little nervous. Besides at just over 50pts it is very satisfying to watch him destroy a Land Raider or Monolith.
I hope this give you some insight into how I play the 411th RCR. They have given me some great success and I always enjoy playing them.