As there is already a tutorial informing us about "Startpoints" their isnt one on how to create it. Though the idea is the same as the one already posted i will try to clarify with ( hopefully ) more details.

The way start points works is that as you are creating your singleplayer map your mission will have different scenes. So it would be then a great idea to have each major scene set up with its own threads. Thus 3 scenes arent in one thread. Then you would just teleport yourself and an ally/allies to an area where that scene would take place and calling in the proper thread to start that new scene. Try and teleport as close as possible to that scene. Why is this important? Because it keeps us from constantly testing everything from the beginning, specially when we just created an entirely new scene and it doesn't waste time as we carry on from our new scene. With that being said let me show you how.

At the beginning of any stock mapname.gsc and before their respective _load::main();, you will see something like this:

    add_start( "nrml", ::normal_start, &"start"    );
    add_start( "brch", ::first_building_start, &"first_building");
    add_start( "dfnd", ::first_building_defend, &"defend");
    add_start( "wave", ::second_wave_startpoint, &"ground_defense" );
    add_start( "bld2", ::other_bldg_starts, &"get_obj" );

        default_start( ::first_building_start );

main()
{
	add_start( "first_scene", 	::awesome_start, 	&"start"	);
	add_start( "second_scene", 	::amazing_action_hack, 	&"middle_scene"	);
	add_start( "final_scene", 	::final_start_hack, 	&"final_scene"	);

		default_start( ::awesome_start );

	maps_load::main();
}

awesome_start()
{
	.....amazing stuff happens then we move on to the next scene.....
	
	thread amazing_action();
}

amazing_action()
{
	.....more stuff to do and we move on to thread 3....

	thread final_scene();
}


final_scene()
{
	......final stuff and we finish......

}

final_start_hack()
{
	//if we have any allies in that scene we want to teleport them first before the player.
	//the reason why is because they will not teleport if the player can see them. Thus,
	//they  must be teleported before the player always.

	price = getent( "price", "targetname" );
	price teleport( ( x, y, z ), ( 0, 90, 0 ) );//teleport( "origin", "angles" ) -- thats how that works.

	wait 0.25;

	level.player setorigin( ( x, y, z ) );// this is where the player would be moved to
	level.player setplayerangles( ( 0, 90, 0 ) );// these are the players new angles when moved there.

	waittillframeend;

	//call on our thread so we can start our final scene.
		thread final_scene();


}

#include maps_utility;

#include common_scriptsutility;

main()
{

	add_start( "first_scene", 	::awesome_start, 	&"start"	);
	add_start( "second_scene", 	::amazing_action_hack, 	&"middle_scene"	);
	add_start( "final_scene", 	::final_start_hack, 	&"final_scene"	);

		default_start( ::awesome_start );

	maps_load::main();



}

awesome_start()
{

	.....amazing stuff happens then we move on to the next scene.....
	
	thread amazing_action();


}

amazing_action()
{

	.....more stuff to do and we move on to thread 3....


	thread final_scene();

}


final_scene()
{

	......final stuff and we finish......

}


/* everything under this line handles our starting points and their respective threads */

amazing_action_hack()
{
	//if we have any allies in that scene we want to teleport them first before the player.
	//the reason why is because they will not teleport if the player can see them. Thus,
	//they  must be teleported before the player always.

	price = getent( "price", "targetname" );
	price teleport( ( x, y, z ), ( 0, 90, 0 ) );

	wait 0.25;// wait this much so that we know the ai teleported safely.

	level.player setorigin( ( x, y, z ) );//players new location
	level.player setplayerangles( ( 0, 90, 0 ) );//players new angles

	waittillframeend;

	//call on our second thread so we can skip the first scene.
		thread amazing_action();

}


final_start_hack()
{
	//if we have any allies in that scene we want to teleport them first before the player.
	//the reason why is because they will not teleport if the player can see them. Thus,
	//they  must be teleported before the player always.

	price = getent( "price", "targetname" );
	price teleport( ( x, y, z ), ( 0, 90, 0 ) );//teleport( "origin", "angles" ) -- thats how that works.

	wait 0.25;

	level.player setorigin( ( x, y, z ) );
	level.player setplayerangles( ( 0, 90, 0 ) );

	waittillframeend;

	//call on our final thread so we can start from the final scene
		thread final_scene();


}