I can't figure out how to use flowgraph to trigger a particle effect and any mission objective from SDK manual.Anyone can link me to a good tutorial ?

How are you trying to trigger the effect and objective? Here's a basic setup using a ProximityTrigger (Rollup Bar -> entity tab -> entity -> triggers -> proximitytrigger).

Done what you said and somehow it is not working.Anyways i'll try to watch some youtube videos since Sandbox 2 isn't that diferent from Sandbox 3.After i walk out a door and step into an area i want 2 effects to be triggered.

And i whould like to know how to start a level with no weapon.Thanks.

LE: Figured out the trigger thing

Starting the level with no weapon is a little bit weird since you'll have no hands but if you want to do it anyway, here is what you have to do:
1. In your flowgraph look for a node called EquipPackAdd and check what equipment pack are you using (Pack = ... )
2. Once you got the name of the pack, go to Game menu -> Edit Equipment-Packs.
3. In the dropdown list shown in the image, look for and select the pack that you are using.
4. Keep ONLY: NoWeapon, Binoculars, PickAndThrowWeapon. Remove anything else.
5. Close window, Save, Export.

Could you explain in detail how have you made it? Thanks.

Make sure your particle is enabled in particle library under database.

Place particle fx into level, and under rollup bar set it's property Active=False

Then use the above graph, should work.