Stay aware of the ways salespeople manipulate you into buying their products.

Stay aware of the “expensive = good” association most people make.
Many of us associate expensive things with good things—we think because something has a high monetary value, it has a high overall value. However, this is not always the case. Before purchasing an item, you should think critically about what its true value is and not allow its price tag to influence your decision.

Stay aware of the contrast principle.
Salespeople often present their most expensive items first, so that you will feel more influenced to purchase their semi-expensive items. For example, you may balk at the idea of buying a suit that costs $500. But if you are presented with a $200 suit afterward, you’d be more likely to buy it as it is still cheaper than $500. Don’t let the contrast principle sway you when you are shopping—remind yourself to stay unbiased.