When I am using charts, I, therefore, do the following:

Stay aware of the fiat price using Blockfolio and Coinmarketcap as when I want to buy or sell a coin I am wanting to make my profit in fiat and therefore track in fiat.
Chart using the trading pair from the exchange where I am either going to buy or sell. Therefore if I am trading NEO/BTC, I will use that trading pair for my chart.
If Bitcoin $ prices are moving, I will take for granted that the BTC buy/sell price will adjust to reflect it.
I know this may feel complicated, but in time this will make sense. The main thing to think about here though is, price in your local fiat and use charts to spot trends.

Anyway, moving on, I am going to use two examples to show how I use trend lines to guide my decisions.