How are home assessments determined?

[Chris Duvall]

I want to refinance my home within the next 1-2 years. How do I maximize what my home is assessed at?

It's a 2 year old cookie cutter in a new neighborhood in Nashville, TN. I have two renters and am living in the 3rd bedroom. I'm likely going to move back in with my parents (who are closer to a new job I'm taking/so I can write off 100% of the home as a rental). 

How does an assessor determine the value of my property? Is it determined by nearby sales within 6 months? There are new houses being sold down the street for 30k more than mine, will they get factored in the assessment instead of my neighbors?

Can I get a better assessment by installing wooden floors upstairs, putting up a fence, "improving" the kitchen, or having a perfect lawn?

Does the home being a rental influence refinancing?

Also, will turning the home into a full rental property influence my goal to get a second mortgage, or will they only factor in my debt to income?

I'm meeting with a accountant next week for rental issues regarding taxes, but a lot of the lending is out of his scope. Thank you all for any assistance!