http://bonyg5gd2cszplkckqffzfcefig5jldgwt36gm2jqdaezlgs3nrfhjid.onion/bible/content/bible/darknetmarkets/making_a_purchase/index.html
Knowing exactly how much to send to the market (cost of product, shipping and commission fees) and having that coin ready is another good practice. Sometimes it takes a while to transfer BTC into a market wallet. BTC is volatile and the price can rise or drop very suddenly, so it is also a good idea to send a little more than expected.