If the luck is on your side and you feel the winning combination, increase your bets without doubts!
There are many blackjack strategies that you may find on the web. Try to specify the strategy that suits you and always follow it!
More info here
There are many licensed and legal blackjack sites where you can try blackjack games online before identifying your strategy for a high stake game
For example: http://casinohex.co.uk/online-blackjack/
When you want to play blackjack, it is better to start with small. Bet $1-$5 to feel the game!
If you lose a lot, stop playing. Blackjack is a game of luck based on random numbers. So it can be just not your day. Try gambling tomorrow!