How can the salesman be observant and discreet at the same time?

He must posess motivational skills, and somehow must have information of particular group peoples wants and desires.

checking customers needs and in the sametime give help to find what they want

ask in good ways.. 

eye contact

1. Use inquiring questions to understand costumer's need.

2. establish eye contacts

3.Suggest product and services.

1. Observe body language
2. Ask indirect questions
3. Analyse trends