When working up a new load, where does one start?

The combination possibilities are huge.

fire arm

Caliber

Barrel length

Powder

Case

Primer

bullet shape, material, weight

For instance, I'm working up a load for a Remington 700 in 300 win mag.

A 180gr bullet will likely best fit my needs. ( and we could probably spend days arguing that point) There are dozens to choose from.

There are 5 different primers readily available

There are at least 8 different brass manufactures

One of my reloading manuals lists 12 different powders and up to 6 different recipes per powder.

If one were to try all the combinations for just one specific bullet you would have hundreds, possibly thousands of dollars and as many man hours invested, attempting to find the "best" combination.

Where do you start?

What determins what components you will start with?

What determins what direction you go after you've begun?

What determins the end point?