How to get a machined part quoted fast

What to send a shop, and the design choices that drive the price.

Send these with every request

A 3D model (STEP is best; most shops cannot use native CAD files) and a 2D drawing (PDF) for anything with tolerances, threads or finishes.
Material and condition, e.g. 6061-T6 aluminium, 304 stainless, 4140 pre-hardened. "Aluminium" alone gets you a guess.
Quantity now, and the likely yearly quantity: setup is paid once per batch, so it changes the price per part a lot.
Tolerances: a general note (for example ISO 2768-m) plus tighter tolerances only on the features that need them.
Threads (size, class, depth), surface finish (Ra) where it matters, and any finishing: anodise, plating, heat treatment, passivation.
When you need the parts, and whether you need inspection reports or material certificates.

Tight tolerances everywhere. Every tolerance tighter than the shop's normal capability adds time and inspection.
Small inside corner radii and deep pockets: they need small, slow tools. An inside radius slightly larger than the tool is cheaper.
Number of setups: every time the part has to be flipped or refixtured, it costs setup time and adds risk.
Thin walls and long, thin features: they vibrate, so they are cut slowly.
Hard or gummy materials (stainless, titanium, Inconel) cut several times slower than aluminium (see the starting speeds table).
Small quantities: setup and programming are shared by fewer parts — try the part cost calculator to see the effect.

Before you send it: check the general tolerance class with the ISO 2768 calculator and get a feel for batch pricing with the part cost calculator.