As the campaign says, if you choose to use them with your opponent, you can take 1 strategem for each 1000 points in your force.
Strategems are split into five categaories: Key Building, Dirty Tricks, Obstacles, Deployment and Armoury.
Key Building Strategems
re-roll failed to hit shooting attacks - not a bad one to be honest, cant kill the enemy if you dont hit them.
counter attack USR to a unit within 12" or auto pass a target priority roll - well since target priority is a thing of the past I guess only the first option is of use.
+1 strength on template weapons - such weapons already have a special place in city fighting, making them tronger is a great benefit.
FnP USR - a field hospital for your troopers, useful for those of us that dont have access to Apothecarys or Painboyz etc.
Re-roll failed to wound shots - a guardsmans dream, but useful for most forces to be fair.
Night Vision and Acute Senses USR's - night vision isnt the bonus it used to be, acute senses might be of benefit depending on the mission and forces involved but I cant see this one getting picked too often.
Stubborn USR - sometimes you got to stand your ground and dig in. Good for forces that suffer leadership issues.
Dirty Tricks Strategems
The IED's of the Grim Dark - not reliable but when they do work they make a mess. I like that they have a chance of affecting vehicles too.
your sappers have rigged one fo the scenery pieces to blow - whats not to love about this, you get to blow shit up.
Barricade those windows corporal! Improve the cover save +1 and gain ignore enemy grenades used for assaulting - this could make a difference in determining who strikes first if/when your poition is assaulted.
Ignore cover on sniper shots - very thematic, reminiscent of one of my favourite movies (Enemy at the Gates), snipers lining up the perfect shot. Not going to be usable by everyone though.
Use vantage points to reduce cover saves - makes perfect sense really, though with the cover rules in 40k sense is a relative term.
Uses the USR with the added chance of damaging ruins/buildings struck too - useful for those forces that dont normally get access to one of these.
Breaching charges for ssaulting fortified positions, wire cutters to tackle razor wire, personal smoke grenades and detonation jammers - probably one of the better choices in my opinion as it offers your infantry counters to many of the other strategems.
Disembark from skimmers onto high level of a ruin - still a risk to do so but cant you just picture your men sweeping in like a SWAT team.
Secondary ammo for your big guns desgned to wreck the ruins of Vogen even more than they already are - used in conjunction with the rules for damaged and destroyed ruins these are fun if not exactly effective.
MC's and models armed with "dreadnought" CC weapons can decided to trash the place - if someone takes this and doesn't cry out "I came in like a wrecking ball!" I'm going to be sorely disappointed.
Barricades, Razor Wire and Tank Traps - already available as extra choices in your forces with Fortifications options but some armies might prefer to field them without paying for an Aegis/bastion/etc.
Deep Strike and Infiltrate - pretty much superceded by the USRs but allow the use of the rule if the mission doesn't already include it.
D3+3 sewer markers indicating spots your non vehicle reserves could come into play from - pretty much a pre-determined non-scattering Deep Strike, good for maybe clearing a kill zone and getting to the enemy with minimal losses.
When these were originally released they (GW) encouraged players to model their own markers to use with them, though they also released a set of plastic tokens for the purpose too (think I've still got the set myself and Gary used to use). Some of the older codex's also included faction specific strategems too, I think the last ones I recall were Iyanden and Black Legion, which had some nice thematic ones included.