Making a natural gravy?
My technique:


1 tbsp Fat (from pan, or use butter) 
1 tbsp Flour  
Pan Juice  
Stock (total liquid about 2 cups - omit if you have enough pan juice)


Step 1: Make Roux


Melt fat in medium high saute pan
Whisk in flour, getting out all the lumps.  (This is called a roux)
Continue to heat until smooth, and the roux is just starting to darken.
Remove pan from heat.


Step 2: Prepare Liquids


Remove solids from roasting pan. (let meat stand... etc.)
Whisk, scrape, deglaze the roasting pan.  If it's brown, you want it, and want it dissolved
Strain juices. skim off excess fat.


Step 3: Assemble


Return roux to heat, and keep whisking.
While whisking, slowly pour in the pan juices.
Once blended, reduce heat and let it thicken.  Salt to taste.