[Iraqiel]

I play a lot of IG and don't often find footguard a 'winning' start point - buuuut if you did want to stick with it, I suggest zulu tactics. The Infantry blob sits near your board edge centrally, preferably holding an objective and with buckets of cover and leadership boosters like priests or commissars. The horns are either attack units like hellhounds and armoured sentinels and bullgryn or are artillery pieces like manticore and your leman russ (no-sponsons Battle Tank is still a favourite of mine). Importantly, you want to be able to keep units relatively dispersed but able to support each other with firepower or (if bullgryn) a charge by turn 3. If you can afford a reserve, be careful that it doesn't compromise your turn 1 and 2 firepower or risk not being able to get to where it needs in time... I find a hellhound or two make a good deus ex machina unit for this.

 

[Iraqiel]

Infantry Guard are exceptionally easy to kill: you'll need a friggin' ton of them to win a match, alternately you need to be facing someone who's bad enough to lose to it. I tried pulling out two 30 man blobs a little while ago with hectic tank support and I got rolled every time by a pal I was teaching how to play the game. It was awesome for him and ultimately fun but I would sell those infantry blobs before putting them back on the table. I don't have the patience for an army I explicitly need 100+ models to play an average game with in a hopes that my opponent is willing to play their army down to my level so I can have fun.

Conversely, my mechanized Guard lists are nigh undefeated in battle and bringing that list allows my opponent to actually play the game instead of walking on the eggshells that are my Guardsmen's broken skeletons.

The Mont'Ka campaign book has a bunch of Guard Formations, one of which is essentially a 50 man Guard blob. Yikes. Another is a swanky Basilisk/Manticore combo with a Command Squad that can issue the Ignore Cover order on any of the tanks from the Formation. Very Nice.

Ntaw says it very nicely there.
The horde of mediocre leadership, T3 bodies does a great job of representing the danger that mortal man places himself or herself in on the battlefields of the 41st millenium... but what that means is that most other units will delighfully chomp down on them.

If you are a chess master and can play them as bait to have your opponent chomp down on then great for you! However, don't think I've ever won a game with a dual blob platoon list, and although I've had fun games they've been fun from a 'desperate last stand' perspective rather than a 'contest between equals' perspective.

Also, it is undeniably more fun moving vehicles and 10 man squads around a table than 30 - 50 man squads... So much time wasted there...