You definitely want to talk directly with the butcher, if possible. This way there is no mis-communication re: what you want. Plus, he will be able to give you some ideas / direction.
Specificity is the key [eg: I want all the suet, and I want it in XX sized containers. I want all the liver in 1 lb packages. I want the shoulders ground up, but the round should be in roasts no bigger than 3.5 lbs, etc]. If this butcher is a pro, he will appreciate the directions. If he seems bothered by your interference or otherwise doesn't seem too interested in accommodating you, that's a red flag to look elsewhere. You're buying 400-500 lbs of meat - it's important that it's cut & packaged to your preferences and needs. What are you going to do with a cow's head or 10lbs of frozen suet? Another reason to talk to the butcher, is you need to know you can trust this guy - you're paying for hanging weight and he can easily sneak 10-50lbs for himself - how would you ever know? Sadly, butcher pilferage is VERY common.
If he tells you he can't give you something, it's probably because he likes to keep it for himself, or it's something he normally sells [like the hide]. It's your cow - all of it - he's just cutting it up, so everything is negotiable. Now having said that, I think it's worth it to pay the guy extra to get exactly what I want. So I let him know upfront EXACTLY what I want and what I expect, and how much I'm willing to pay for the special handling.
As for what to get, I take it all [except tripe [stomach], intestines or the head/brain. I think after BSE there are regulations re: the brain & spine. I could be wrong on that. Tripe is tricky to clean, cook, etc].
Definitely get the liver, kidneys, heart, tongue, cheek, sweet breads, ox-tail, beef fat, suet, all the trimmings, marrow bones, soup bones. Specify that the bones need to be cross cut to XX inches. Otherwise you may end up with uncut bones, which are huge [I learned this the hard way].
As for the cuts to get, that is just personal preference. If you have preferences, spell them out very specifically - don't assume. My son gave vague instructions this fall and ended up with 250lbs of ground beef [~65% of total]. I prefer roasts and thick steaks, each individually packaged. I want my ground beef in 1lb paks. I try to keep my ground below 30%, so I have him make steaks and roasts out of stuff that may otherwise get ground: round, chuck, shoulder, cross cut shanks, brisket, flap, flat iron, hanger, skirt, etc. I also specify to leave the bone with the back rips, short ribs, etc.
Tons of info on the web re: different cuts.
Hope this helps. Follow up to let us know how it turns out for you.