Ok to kick off Iron Hands tactics, we bring in the fitting Tactical squad. Let me start of by saying you will probably want to be maxing out these squads to leverage Involite Armour (rhinos and transports don't get it). As you will want to be out of the melee taking extra combat weapons probably isn't the best way to spend points, and replacing your bolters is down right illogical. For the sergeant a Combi Melta is probably a good buy, as a way to have a chance to remove enemy Drop Pods. Giving your sergeants a Cyber Familiar is nice but he will only gain a 6++ (he can also reroll statistic tests but meh) which will bring you on par with SOB/Adeptus Sororitus. It should save you 1 in 6 sergents but you should only be buying this on your sergents as points filler (great of commanders and terminators). A Legion Vexillia is an excellent idea as your army has no built in morale boost rules. This wargear allows you to reroll morale checks and leadership which is great when your marines have no ATSKNF. Watch out for recons with sniper rifles they will want to execute this guy first (this guy gives LD reroll which is better statistically much better than the LD9 from the sergeant).
Assault squads, your iron hands don't kid your self, you can't use what they're good at. You can't sweep well (LD check to sweep) with them, they are part of the restricted units as of Rigid Tactics (bikes are a much better choice with t5 and -1str from shooting against them), nuff said.
Support squads: great option but they don't count towards compulsory troops so you will need to take Tacs to field these guys (can still score). With the Iron Hands rite of war support squads can swap their flamers for gravitation guns. In drop pods these guys will shred Spartans even with flare shields as Haywire isn't effected by Flare Shields as it has no Str, forget suicide melta squads. Plasma is very effective as an terminator deletion squad, but it is very expensive. The Volkite long range heavy weapon is brilliant with a range legion.
Recon squads: with sniper rifles and 3+ armour these guys are really awesome for a shooting legion. Precision shot is execellent for erasing Vexillas, Nucio voxes (for iron warriors and other ordnance armies) which are often better choices than sergeants. With rending artificer armour is rendered redundant of sergents. Also use these guys to remove special weapons in veteran squads. Like support squads these guys can't be compulsory troops. With camelon cloaks and the -1str for shooting against them and a 3+ save you can make these guys very competitive when supporting a good list.
Drop pods are dangerous for IHs because they can't sweeping assault very well, and they will be in combat where the -1 Str shooting won't help you. Iron hands don't want to be up close.
Rhinos and other vehicles can purchase a 6+ roll, that works in the same way as IWND, but as its seperate from IWND you can get two of these rolls by including Ferrus Manus in your army. This is great but as vehicles don't benifit from Involite Armour you can't leverage this rule, use mech when you need to. You don't want to be close, making the speed of a vehicle redundant, and you can't shoot the squad out of it, also making the vehicle redundant.
That's my take on Iron Hands Troops. I recomend 3+ armour recons with sniper rifles and camelon cloaks, tactical squads with combo meltas, artifer armour and Vexillas and Tactical support squads with either suicide grav or plasma (anti vehicle/ terminator respectively) or long range Volkite.
'Rest? We were not made to rest; we go on, unflinching, unstoppable, unending in our strength. The Emperor did not make us for such mortal concerns as hearth and home, vanity or contemplation; we are his engines of war, his hammers, beating out the fabric of existence into a vessel fit for Mankind to inhabit.'
— Ferrus Manus, as quoted in Shadow of the Gorgon by the Remembrancer Czel Atternus (from Horus Heresy Book 2: Massacre, page 234)
Quote thanks to Warhammer 40k Quotes Facebook page