What is the proper way to prepare a solution aiming to minimize errors? I am a undergraduate student in chemistry, and my university is very weak in teaching solution preparation. I need to prepare a 10 mg / L methylene blue solution and now the way I do is, using an analytical balance of 5 decimal places, I tare a 50 mL beaker and simply add the 10 mg of methylene blue, trying be as accurate as possible (the amount is very small due to the large molecular weight). Afterwards, I add deionized water to a certain volume and transfer to a 1 L volumetric flask using a funnel (I wash the small beaker several times to guarantee that I transfer as much as possible of the compound) and complete with deionized water until the meniscus line. And so, I shake it many times.

Is this procedure correct? If not, how can I prepare this solution avoiding errors?
Methylene blue isn't a primary standard so I'm not sure how much accuracy/precision you need. 


Typically when wanting the best accuracy the solid would be dried in
a hot oven, then cooled in a desiccator.
Do not to handle the beaker with your hands. Even if it has been
"left out" in humid air that amount of water would be stable. So use
tongs to pull in and out of balance.
Another option is to weigh more and do a serial dilution. So 1 gram
in liter, then 10 ml of that solution into 1 liter.