Signs of a trend:

• Each low is lower than the previous one in a downtrend, and each high is higher than the previous one in an uptrend.
• In the case of a trend, the upward or downward tendency is constant. For example, if looking at the hourly chart, a sharp price increase within a few hours is not a trend. However, if a constant price increase is wave-like, it can already be referred to as a trend.
• Price retracements in relation to its major movement are usually minor, and the price quickly comes back to its previous values.

We can also note some characteristics of a trend that are not mandatory but can be observed quite often.

• Trend often starts with a strong price impulse and ends in the same way.
• Before the opposite trend begins, the price often goes into a flat state, staying in it for some time. The given price behavior may be a signal for profit-taking.

Keep in mind that trends may differ in various time-frames. For example, a trend may move up on the daily chart, while falling on the hourly chart. In this case, the higher time-frame has a higher priority, but short-term bearish trades are allowed if focusing on the hourly time-frame.

Do not forget that the price can change its movement direction when it hits a significant level on the daily time-frame.

int TrendMA_Period = 13;     // Averaging period for calculation.
int TrendMA_Shift = 15;      // Shift relative to the current barto compare the averages so as to determine the trend.

TrendUp=(iMA(symbol,period,TrendMA_Period,0,MODE_SMA,PRICE_CLOSE,iBar)-
         iMA(symbol,period,TrendMA_Period,0,MODE_SMA,PRICE_CLOSE,iBar+TrendMA_Shift)>0);
TrendDn=!TrendUp;