Optimising scenes. Help appreciated.

Right. First post, so feel free to tell me to go away and google… though i’ve spent days searching for info and couldn’t find anything concrete.

I’m basically after improving the way i handle scenes from a point of view of performance, so any tips on how to do it appreciated.

What i’d like to know, is if there’s anywhere were i can see how different ‘effects’ (don’t flame me here, i’m spanish and have troubles finding the correct terminology) affect performance.

For example:
Which is more efficient, to use blender generated textures or using UV images?

Is there any advantage from a performance point of view to join multiple objects into a single one or it won’t matter if the resulting object have the same number of vertices?

Linked duplicates better than normal duplicates?

What material/texture variables require more ‘power’? I now transparency/mirroring/raytracing probably top the charts, but are there any other i should stay away from if at all possible?

Obviously complex meshes will suck more juice, so, any way i can take an object and make a lower quality version of it without having to remodel it from scratch so it can be used when it’s on the background?

If anyone would like to have a look at an example of a test i’m doing you can download the .blend at megaupload, file extension ?d=BUP8ZJPP.
It was too big to attach to this post. Maybe an indication of my slopiness? :o
The file is safe BTW. Not trying to trick you into downloading some nastyness.

I’m aware of the use of layers. Haven’t done so here because i’m trying to to find the most efficient way to handle a single layer before i start using mutiples.

Please have a look at it and give me some criticism.

The scene as it is takes over a minute to render, so not a powerful computer here.

Thanks guys.

The Avenger