if you dont know the fight and your raid buddies doesnt do a good job explaining

visit sites like bosskilllers.com can be great help

and try start with normal mode first - its not 100% the same as heroic, but you will get a basic understanding how the fight goes, and how the bosses react

going straight headed into hardmode clueless is only advisable if your entire guild is well-geared, and you guys have good understanding on each other's skill - which is why most hardcore raiding is extremely taxing on both your skill, gear as well as your wallet

accessible raids are much better idea than a super tough raid that only 10% of players ever get the chance to get inside - MC, AQ, and original pre-60 Naxx for example

if challenge is what you want, there's always hardmode that wipes hardcore guild for breakfast