Whats the best way for me to minimize fees when transferring from coinbase to polo or bitttrex.
nothing!Quote
also my understanding is when i want to take usd from alt coins, i first have to convert it to btc then to usd? what would be the best way to do that to minimize fees.
depends on the altcoin. some of them have markets against USD, for example Liteoin has LTC/USD in coinbase you can trade there directly.but for most of them there is no other way, you have to trade them with bitcoin and then transfer that bitcoin to coinbase and sell for USD.
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also when transferring from an exchange to my offline wallets will that also cost a fee?
yes but that is a fixed fee. usually a different amount based on which exchange you are using. some of them have 0.0025BTC fees (kraken) and some still have a small fee of 0.0002BTC (c-cex) 
