[Is there a Dewalt guide rail for the DEWDCS570N circular saw]

Look for 

1. .torque and speed

2. Type of grip

3. Weight and comfort

4. The capacity (drive size)

5. Battery size 

6. warrenty

[20V Impact Wrench]

I would suggest for AVID power 20v max impact wrench, as its a best seller in amazon , as its a powerful and budget tool . but if you are looking for more powerfull tool then i recommend to go for eneacro cordless max impact wrench which is more powerful when compared.

 Hope this helps

[Tool Buying Guide.. (For the Beginner)]

Great thread Comp, also i would like to add Design and ergonomics should be considered along with the Power i.e Variable speed . and type of motors used. should be checked before buying a tool. hope this helps

[Brand new to woodworking!]

New to woodwork??  The basic and utmost important step is the safety and handling of the tool.  Il mention some of the basic safety procedure here and they are

1. Follow the user manual and handle the tool with care.

2. Dont expose the cords to heat and oil when not in use.

3. Never ever carry the tool a tool with the hose or cord's

4. Keep all people not involved in the work place away, especially children's

5. Disconnect the tool when not in use.

6. Wear proper gears while working , avoid jewels and loose clothing

 

Hope this helps