Hi Carlos,
I don't know how fresh the seeds of Alstroemeria presliana were, I bought from Ebay at the time.
The substrate I used was good potting soil, nothing special. I didn't use any specific trays either, they got planted in small plastic pots under growing lights in a room-temperature (20-22C) heated room.
Pinching a hole in the seed with a needle and soaking in warm water obviously has obviously speeded up the germination process, rubbing with a sandpaper could also have worked I guess, the purpose is that the water can penetrate the hard seed coat.
I must have got my info somewhere from the web how to germinate Alstroemeria, so I guess that is why I also gave it a two week treatment in the fridge.
I have also read somewhere that Alstroemeria seed can take up to one year to germinate! maybe I was just lucky or it is that particular type of Alstroemeria.
It was my first time I grew it from seed, so I cannot give you more info..