What yeast strain did you use? Usually, the best fermentation temperature advice comes directly from the yeast manufacturer's website.
If you're using a lager yeast strain, those are fermented at about 48-54 degrees, depending on the actual strain.
Those instructions are terrible- but I'll tell you why they say what they do. Since lagers are supposed to ferment at 48-54ish, it's important to use more yeast than you would in an ale. Most stores don't tell you that- so they'll tell you to keep it warmer until signs of fermentation have started and then lower the temperature to the desired fermentation temperatures. This sort of works- it allows the yeast to reproduce at a warmer temperature so it increases the yeast cell counts- and it might not make it taste too off if you manage to lower the temperature fairly quickly once signs of fermentation start.
No one will tell you that it's the BEST way to make a lager, even though it might work. Just like I don't start an ale at 85 degrees and lower it to 65, I don't pitch a lager 20 degrees too warm either. Sometimes, fermentation can take off and most of the fermentation can be done before you even get to the proper fermentation temperature. Or, you can stall the fermentation from dropping the temperature too quickly.
Usually, a lager needs a large starter because of the cold fermentation temperatures. After about 10 days of primary at 50 degrees, the temperature can be raised for the "diacetyl rest".
Diacetyl is a by product of yeast, and it's more common in lager strains. What happens is the yeast produce diacetyl (especially lager yeast at warm temperatures- another reason why a cold pitch is better in my opinion) and then when fermentation is over, the yeast clean up after themselves and go back and eat some of their own waste products, like diacetyl. Diacetyl has a slick mouthfeel, and a buttery or butterscotch flavor in large doses.
To do the diacetyl rest, when the lager is 75% of the way to FG, the temperature is raised 10 degrees. That will cause the still-active yeast to be encouraged to clean up the diacetyl when the fermentable sugars are gone. Raising the temp when the lager is at 1.020 or so won't cause the esters and off-flavors that it would early in the fermentation, so it's a good time to do it.
After the diacetyl rest, the beer is racked off of the yeast cake. Then, it's placed in a cold place for lagering. I like to lager at 34 degrees, for each 8-10 OG points. So, for a lager with an OG of 1.060, I'd lager at 34 degrees for 6-8 weeks. Then, bottle.
