Toploading Balance
These balances accurately weigh objects with masses of up to 300 g  to two or 3 decimal places; that is to 0.01 or 0.001 g  (1 mg).
At a sensitivity of 1 mg, this balance is very susceptable to air currents. However at sensitivity of 10 mg, it is much less sensitive to most normal air currents and/or "leaning on the bench".
Using the Tare
Pushing Tare sets the balance to 0.00 g.
Put a container on the balance pan and press Tare. The balance will read 0.00 g .
Add material to the container. The balance will read the weight of material added to the container directly. No need for subtraction.

In the above picture, if at this point you pushed Tare, the balance would read 0.00 g. Removing the flask would then make the balance read -157.40 g because you set it to read 0.00 g with a 157.40 g mass on the pan.
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Electronic ANALYTICAL Balance
weighs up to 200 g.
Reads to 0.1 mg, (4 decimal places in g).

• Always zero the balance before using.
  Make sure the balance is level.
  Never lean on the bench while weighing. The observed weight may be in error due to the very slight tilting of the table.
  Keep the balance doors closed when weighing. Stray breezes will cause significant fluctuations in the weight.
  Analytical Balances are delicate instruments. Clean up any mess you make.