Best way to start is to get a few dealers to give offers online against each other...sites like edmunds.com or kbb.com can help with that.
If you go into the dealership...some things to remember.
1. leave you emotions at home...never make a decision while being emotional...although, it is hard to resist that new car smell.
2. Always be willing to walk away if you don't like the deal..always.
3. Focus your negotiation on the price of the vehicle out the door...never let them work around that number by offering you a low monthly payment. Settle on a price before any rebates, etc.
4. Be willing to visit (if not doing online) multiple dealerships...get them to fight for your business.
5. Take a friend...perhaps someone who has some experience negotiation for a new car...someone good at it.
6. Research, research, research...there are many websites (like the ones above) and tools that should give you an idea of how much the vehicle cost (msrp and invoice) and how much each option or option package cost. Never go in ignorant of such things.
Many here have gotten their 4Runners at around or below invoice...which is way below MSRP. So, it can be done.
good luck.