ASOS quite often have promo code. You can always receive it by emails. Promo code normally can be used on both nomoral price clothes and those on sale ones. As I had busy life and didn't check my emails very often, so quite often I missed...
The clothes in ASOS are updated very quickly. ASOS is a very flexiable company. No matter how high the orignal price or how good quality for a cloth is, as long as it's not selling well, the price will drop very quickly (25% to 50%). I did choose some very good quality clothes from those not so popular ones (personal perference is also very important). However, The price for some classic designed dresses for work or party can be quite stable ( may only drop 25% until it is totally sold out). so it's hard to answer your question. It really depends...
I would like to suggest you regularly save whatever you like first (especialy from New In Clothing), then everytime, go to your Saved Items to have a quick look first. From there, you can find out easily the price for those clothes your have choosen drops or not. Also, if you see anything (you have saved) is " low in Stock" ( ASOS will send out this warning), you'd better check it out if you really like it. Popular clothes can be out of stock very quickly.
I would not suggest you always go to sales products unless it's on seasonal sales like currently Christmas sale. To choose whatever we like is always most important.
Hope the above information can be helpful for you.
Have fun!
