Need render tips for a slow computer
 

Hey everyone. I am still very new here but I am moving out of modeling and textureing into lighting and rendering. It is going pretty slow because when I render a scene I have to wait for everything to render through. It can be time consuming with such minimal adjustments each time.

I have 2 examples of things I've done in Lightwave that I would like to transfer to Maya:

I have a scene with a table, table lamp with 2 spotlights in it, and an envelope on the table. Is there a way I can render just the table and spotlights but still use the lamp's shape to cast shadows on the table?

Can I turn off one of the lights without loosing any of it's settings. I guess similar to flipping a lightswitch. The light still maintains the same intensity, falloff, etc. except it's just not being used.

Any other tips to help my process along here would be greatly appreciated.