Canon Canoscan 8400F workflow

[lost]

I finally bought a scanner that can do negatives. I have a couple questions.

1. Negative Cleaning and Handling Precautions.

2. Best Resolution/Size to scan 35mm and Medium Format(120)

3. Should I scan from Photoshop?

I am new to this and will appreciate the help. I will post some examples when I get started.

Thanks