It has now been a full expansion plus the preceding raid tier (Dragon Soul) that we have had access to LFR. Generally I am not a fan of LFR. I prefer normals or the spiffy new flex. I want to raid with my guildies, who are skilled and fun to raid with. However, the Wrathion legendary quests have required some LFR and I have done some in general for gear and valor points. When I zone into any instance I have a few expectations. No matter if it is a scenario, a 5man dungeon, or a raid, I expect that the people there have made some sort of effort to learn and equip their class. I still have these expectations in LFR, though my standards are a bit lower.
Wear appropriate gear. If you are a tank that gear is likely to have some combo of mastery, dodge, and parry. With haste for pallies and crit for bears and monks.
Make sure that the gear you will be wearing is gemmed and enchanted. It doesn't have to be perfectly optimally enchanted; some of the weapon enchants are expensive, and this is just LFR we are talking about. But you really, really need to have gems in all your sockets.
Check your reforges (in combination with your gems) and try to get the correct amount of the right stats. Ask Mr Robot is helpful for this, as well as several auto reforge addons. If you don't like Mr Robot's stat weights at least use something else to make sure you're hit/expertise capped.
The important thing (and what sparked this post) is that when you queue for LFR you're signing up to be there until the last boss of the wing is dead. Right now in Siege of Orgrimmar the queue is tank blocked. So if a tank queues and then drops after one or two bosses the rest of the raid is left sitting there twiddling their thumbs waiting and waiting for another tank. When you click that tank check box you're saying you'll be there for the wing. You're not saying that you'll flake after the first boss doesn't drop the loot you want.
I thought that the above expectations weren't excessive, but my experiences in LFR recently have proven me wrong. The dearth of tanks in LFR seems to be caused by a large number of tanks randomly dropping after a single boss or a single wipe. Some of them left the raid after being embarrassed when they were called out for dying too easily and it was pointed out they had no gems or enchants. In the five LFR I've run over the past two weeks I've not completed a single one with the same two tanks that it was started with.