I found Bollinger Bands (to buy) and selling based on your decided profit target as the best strategy working out for me. I will try to explain the whole concept below:

Intraday Trading on exchange - You can register on exchanges like bittrex or poloniex and start trading in USDT/BTC. Follow the below strategy:

Buy Bitcoin in cash from your friend/relative or you can use Blocklinks app Blocklinks - Android Apps on Google Play
Transfer it on exchange - Poloniex or Bittrex.
Convert your BTC to USDT. Note: USDT is a crypto currency that represents USD and its value is also kept near to USD.
Trading Strategy - In trading always create your profit target. If you won’t do it then you will always lose. For example -
I created a profit target of 5-10% monthly trading USDT with BTC, ETH, XMR, ZEC and DASH.
I invested around 3,530 USD and divided my investment in following way: BTC - 39%, ETH - 39%, ZEC - 7.5% ,DASH - 7.5% and XMR - 7.5%.
Now in each currency I always trade 25% of total investment assigned.
The trading strategy used is bollinger bands. (You can create bollinger bands on graphs in poloniex). The strategy is to buy when price touches lower bollinger band and sell when the price is above your bought price and also hits high bollinger band. If the price goes down and again touches lower bollinger band then invest another 25% of total investment assigned for a currency.