Josh Ledgard from Microsoft has an interesting "5 Tips for Being Successful at Microsoft". I think it applies just as well to IBM.
The "ignore artificial boundaries" post was particularly relevant. In my current role, I am working on a project that requires me to have regular and in-depth contact with the development and test teams of a forhcoming product release. As a field consultant, it's unusual to have quite this much contact for so long. I have to keep fighting my natural instinct to leave them alone and let them get on with it.
I'd qualify point 5 ("talk to customers") a little, however.... yes: our developers should talk to customers as much as humanly possible.... but make sure you're talking to the right customers! The customers who come to the lab for a three day briefing with a delegation of 10 staff are important; but so are the small customers.... the ISVs.... the business partners and the hobbyists. Getting involved with mailing lists, message boards and local user groups is as phenomenally important as sitting in on those briefings.