I'm late to the party, but I'd like to chime in here.
My approach sort of splits the difference between J. Scott and what Financeautomaton (Just breaking your nuts a bit there) suggest...
I also come at this from a slightly different perspective, having done BPOs for awhile back when the money for BPOs was still good. It's not appraisal experience, but the process of doing a good BPO is a lot like doing an appraisal.
Anyway, to get back on point - I don't like to meet the appraiser in person. I know when I did interior BPOs it made me very uncomfortable when someone was following me around, trying to talk the subject up. I also know that most people in this business are either very talky or very shy... and that an appraisal needs to be data-driven.
Either way, I never have felt like an appraiser needed to be chit-chatted with while I pointed out how tremendously awesome my trim carpenter is. "Check out the way he coped that joint. That's worth at LEAST another 5 grand!"
What I do, however, do is this -
Prior to the appraisal even being ordered, I put a CBS code on the supra box and keep it a closely-guarded secret. Not even the buyer agent is going to weasel it out of me. I also put out a contractor box and change the code every time I give it out. I ALSO tell the lender directly that the appraiser must call me for access... in other words, until he talks to me, Jesus himself ain't getting entrance unless he brought along a master key.
When I talk to the appraiser, I ask him some very carefully-worded, very on-point questions -
"How are we looking for comps?" (The answer varies, but most of the time they haven't even started on data-discovery)
"Have you been given the contract price?" (the answer is always "no")
"I have information regarding the renovation and some possible comps. Would you like me to send it to you?" (The answer is ALWAYS yes. Half the time the appraiser thanks me for getting half his work done for him)
And then it's very mundane - I get his e-mail address, the best phone number to call if I need to get in touch with him, and then... ONLY THEN... does he get the CBS/Lockbox code.
My data package is a lot shorter than J Scott's. I give the highlights of the rehab (Rewired, replumbed, new HVAC, etc.) and a short summary of the major expenses involved. I don't get nearly as detailed as J does.
I do, however, state that receipts and a ledger are available if the appraiser would like to see them to verify numbers.
(Side note... I once had an appraiser call me and say, "You didn't REALLLY spend that much, right? This house wasn't in that bad of shape. You're just puffing."... I very quickly, without hesitation, told him that YES I DAMN WELL DID and that I was ready to show him receipts. He then laughed and I asked if he was just trying to see if I'd blink... he said, "Yeah, I was. You'll get your value"
Appraisers can be real jackasses.)
I also provide a copy of the certificate of occupancy and a short-form BPO showing up to 5-7 sale comps and 3-4 active listings.
I also take the time to pull permit records on the sale comps... in lower-end markets, most of them have no permit record and I can therefore make the argument that they have not been rewired, replumbed, or even had a new HVAC installed (Government evidence to that point being missing. If they had that stuff, they'd have had permits... right? right? wink wink nudge nudge)
While I haven't had an appraiser directly confirm if the permit/no permit thing influences them, I will say that since I started using that tactic I haven't missed an appraisal yet and I've had to spend a lot less time haggling with the appraiser.
Maybe our appraiser friend here can lend some insight on that issue?
The times when I have had an appraisal come in low (It happens), I've had good success pushing back on it and having the appraiser redo his comps. Typically the lender is on my side in the matter, so that helps.