First, it helps if they make more money for each admit. The owner of the hospitalist group will take any admission and trolls the ED for more. If he can justify it, he'll take it. His employees, not so much. They'll take the admission, but it's almost passive aggressive- they take 2-3 hours to get the orders in sometimes. But I know who to call....he just has a hard time hiring.
Second, get to know them all personally. That helps.
Third, don't blow smoke. If it is a soft admission, tell them. If you just can't figure out what to do with a guy, ask for help. If it's general surgery or ortho dumping on them, tell them that. It's a short term relationship with the patient, but a long-term one with the hospitalist.
Fourth, be competent. Don't be that guy who's always forcing them to take an admit. If you find you're arguing with them every week and your partners rarely are, you might be the problem. Know what needs to be admitted and what can be worked up as an outpatient. Just because you admitted a bunch of chest pain in residency doesn't mean that's the way it has to be done at your new shop. Maybe at your new shop the incidence of CAD is way lower and you can get a 1-2 day stress test easily.