My check list:
1) Find out who all your vendors are for internet
2) Check performance to date and compare over the next 90 days while you are there (Just because something wasn't performing doesn't mean it isn't good.
3) Call your reps of these vendors and introduce yourself. Tell them you would like to be trained on the product and that you will be reviewing the account over the next 90 days to see how they perform. If they are any good they will jump through hoops to make sure you are successful with their product.
4) Figure out how much you are paying for your vendors and contract terms (Have the rep bring this to you when they train you)
5) Network on here and build relationships with the people who know what they are talking about.
6) I agree with Joe. Your problem is within the organization. Maybe it is gone already but whatever it is don't concentrate on the problem. Set your goals to be reachable for next month. Pull a report and see what they did last December and go from there. Keep reports on sales you have produced in case it comes up in a meeting.
7) Do searches for your dealership and find out what is out there (Bad reviews, scam reports, good reviews, etc...) Maybe someone is buying your dealer name in a ppc campaign.
8) confirm all numbers are right on website and in google local.
9) Go through your website and confirm all information is up to date.
10) Go through the CRM and see if there are any resources you can use (Email Newsletter, Blast Email Update, Current Client List, etc...) Send the sold clients a letter introducing yourself and explain that you are there to assist them and their friends and family. Send out an email to the current prospects and introduce yourself and let them know you are new and you do things differently and will be offering a special....explain the special you can give. Ask them why they didn't buy before from your dealership. Feedback may help you determine why the dealership isn't doing so well. Lack of follow up is normally the answer. "No one called or emailed me back". Thats my experience.
11) Maybe a little early but I would also pay someone else to do a ppc campaign for me. Joe knows someone he can recommend.
Thats my top 11 starter kit off the top of my head. Good luck!