This is a bit more of an open-ended question than you think, so I will not be able to give you a definitive answer there, but I can try and help give you some insights.
Regarding behavioural patterns, the idea is that price action will reflect the general psychology of the market participants given available informations.
That is true in the case of determining a “fair” price (say, Netflix just reported a loss of subscribers, and almost immediately the price stabilized down, finding an equilibrium agreed on by every market participants).
An other type of behavioural pattern, more closely related to TA, would be Fibonacci retracements, or supports and resistances.
Let’s look at these two examples; in the case of Fibonacci retracements, which are based on the Golden Ratio, to some extent, actors in the market will unconsciously favour a price retracement lining up on Fibonacci values, the cause of it more likely to be a subject of human psychology. Some people having observed that, started to graph on their chart such levels, and trade accordingly, in an increasingly more automated manner. This leads to a self-fulfilling prophecy, as more and more trades are conducted at these levels, making it even more observable.
In the case of supports and resistances, it is a bit of the same. If a certain security have had lots of trading activity happening at a certain level, when the same level is reached again, lots of actors will have a psychological barrier that said price is somehow important, and they will place orders accordingly; thus rendering it a price level at which lots of orders are waiting to be consumed in the trading book, and thus creating a support / resistance.
If you want some “effective TA”, that will yield you some results, the key will be to see what other participants see in your charts; if you think many people believe X price cannot be broken easily, you may try to profit from a large number of orders waiting at this price and the resulting reversal. If you go and start looking at increasingly more complex and obscure candlestick patterns, chances are you will be the only one seeing it in you chart, and your prediction of what happens next will be flawed.
EDIT: Got lost and forget about your second question. There will be no good answer for a stop loss level. This will have to be determine based on your capital reserves, the volatility of the trade, and the reason why you enter the trade. If you enter a trend-following trade, your stop loss should reflect the question “At what price is the trend broken?”. In general, the question would be “What would invalidate my trade?”, and this should give you an idea where you would want your stop-loss.
Now, trading with indicators, you would likely look at a statistical benefit, for a strategy with a certain % success. You would first look at your take-profit price, and then at the stop-loss. You need your ratio of profit over loss, based on your % success rate, to yield a positive result.
That means that some trades, you will have to not enter, if your stop-loss has to be much bigger than your take-profit would be.
