With the recent hacking activity, and account locking, the only safe way to send Steem or Steem Dollars to bittrex, or any other user or exchange, like 
In order to use that.. you will probalby need your windows miner which will be updated soon to 0.11.0, or a linux miner-seednode...
Go in the Cli and type
gethelp transfer
after that, the cli prints, the following result.
Transfer funds from one account to another. STEEM and SBD can be
transferred.
Parameters:
from: The account the funds are coming from (type: string)
to: The account the funds are going to (type: string)
amount: The funds being transferred. i.e. "100.000 STEEM" (type: asset)
memo: A memo for the transactionm, encrypted with the to account's
public memo key (type: string)
broadcast: true if you wish to broadcast the transaction (type: bool)
Than means in simple words...
transfer myaccount receiveraccount "100.000 STEEM" memokeyprovided true
transfer steemychicken1 bittrex "100.000 STEEM" memo true
Thats all!