A big area that can show your commitment to raiding and make you feel more comfortable in an encounter is some upfront research. Some people learn differently than others so there are a few methods I would recommend pick what works for you.
If you have not ever raided before then many of the concepts can be rather challenging and the encounter details rather long, so try not to get overwhelmed by all of the detail.
For most players actually playing in the raid for the first time will provide the most learning, but doing the research ahead of time will give you the tools to understand the pace of the fight.
The Dungeon Journal, not just for dungeons, this includes a host of information that is quickly broken down; and major abilities are called out. If you do nothing else you should at least read this, and focus on your role in the encounter.
FatBossTV are the authoritative video guides and do a good job breaking down the mechanics, these are often released right at the start of a raid tier, so the strategy they suggest might not exactly match the real world tactics from your guild so defer to the Raid Leader, but it should give an overview of the mechanics.
Wowhead Raid Guides, also written by the FatBossTV crew they are longer form and go into very deep detail on everything going on, they can be hard to parse if you are new to the encounter but can provide very good information.
A good place to start is with the Role Responsibilities section and then work backward.
LFR, if you have the time LFR can give you an idea of the general flavor of the fight, this can be a bit of a hit or miss scenario as LFR is often missing at least one major mechanic but it can give you a good baseline for the pace of the fight in general.
It can add some context to the above methods, but you shouldn’t expect LFR knowledge alone to be enough.