How to start? The very begining.

First, what you do, when you start: immideatly go and explore arround!
You crashed at the day time; and the day time is THE BEST time to go arround, when it is still quiet. And you can not go and explore after you dump all the resouses here: it'll be the night time.

Don't start gathering at the crash site: you will be able to do it at the dangerous night time that comes in a minute. You need to pick up some bonus supplyes to "get permition" to build a protection turrel. Defenitely, you will pick up some "bolls" with a lot's of minerals or gas, so you can only win by explorung surraundings.

Then you come back to the crash site and heal youself while simunstinuosly building one or two protective turrels. After that (at last!) you can pick up minerals at the protected site at the night time... well, unless not familiar with winning strategy guys did it during the first day.

In addition, you can be lucky enough to find some Factory and kill it's gurdians (by setting turrels neaby and reparing them(right click on your repare icon gives you autorepare)) while Rouch attack the turret. Or you can come close, tuch the factory, command your SUV to run away far enough from chasinf Zerg and quickly take away the factory from there.

Now you can set you temporary camp near Mineral Fields: few turrels and storrage, few mules to help, and start gathering resourses.

Factory - this is something that you need in order to build a few mules, which will gather resourses for you and repare you instead of healling at the crash site.

It is good to give them outorepare too: by right clicking on repare icon in their meny.

Now you don't need to go to that Crashing Site any more.
After you pick up a few touthends minerals and some gas, you can go to a safer place (big hill) and start esteblishing you defence there.

It is good if there are some resouces there, so you can hurvest in safety with mules while you are building defence.

Don't build a Saving Ship or Saving Beacon before your defence is built: Zergs will send big monster to stop you. Unless you can defend youself - they will destroy your saving plans.

Note: this is pre-patch 9.0

In my early game I leave immediately and scout around for a good source of minerals, a gas geyser, or a factory. The first night you should need no defense other than your Lasgun, and should be happily mining minerals. By the second night, set up a turret and some barricades for defense, and ideally have found a geyser or factory. By the third wave (Banelings), I would have used 1-2 turrets to clear out the Spine Crawler/Hatchery near the gas and would be mining it/mined out. If you or your allies have found a factory, I buy a Mule to gather minerals while I mine gas. I then use the next day to relocate to high ground. I establish myself atop a ramp and set up a wall of barricades/bunkers backed by four Auto-turrets and possibly a Siege Tank. Ideally for the hydra wave, I would have my Mule on auto-repair, the "back" of the base secure, (I only have one ramp defended, but often the Zerg completely ignore the undefended entrance.) and am mining away on whatever resources are nearby with my SCV.

This is my usual progression.