EVALUATE AND UNDERSTAND THE CODING
If taking another persons code it is important to understand how it works, which indicators are used and to get to a point at which your are able to explain what it is trying to do to someone else. By growing you knowledge of the code you will being to develop the ability to produce your own code from someone elses ideas.
TESTING AGAINST MULTIPLE MARKETS AND TIMEFRAMES
A robust strategy should work in multiple markets and timeframes, otherwise it may be over optimised and not a good long term prospect. Having a portfolio of strategies that cover multiple products and time frames can also add a level of diversity that reduces risk of the overall portfolio.
THE IMPORTANCE OF DIVERSIFICATION
Diversification between products and time frames allows for a portfolio to be produced with less volatility and systems cover both long term trends and capturing sharp movements such as news events. All systems will at some point have stretch of losing tradings and over reliance on a small number of strategies increases the likelihood of losing your capital.
MONITORING LIVE STRATEGIES
When taking systems live it is important to check that they are still producing the expected results. It may be that your system only makes a profit on 40% of trades so starting off losing money can happen but that can be the expected result. No system will make 100% of winning trades.