Hi ! I buy from time to time some stuff on AliExpress.
There are a few tips that I want to share.

Keywords for research

First, take the time to choose the keywords and test. Some items have different meanings try in English, in Chinese also.

Login when you perform your searchs

AliExpress has a very well implemented Cart and it records your searchs. It is very helpful, my Cart is usually populated during weeks/months. So you can take the time to search, to compare and to refine further. You will not loose the content of your Cart.

Sorting Items by number of Orders

Most of the time I sort by the number of Orders, not by the price. Historic of sales is helpful from a risk point of view.
After I go on the shop and I sort the items of the shop by the number of Orders too, to have a look on what is worth or not, it gives also an idea if the vendor is serious.

Shipping

Shipping also is a main concern, I strongly advise to use shipping with tracking, in case of issue. More important, you need to change the quantity of the good you want to buy to check how the shipping cost change. With some vendors, the shipping cost goes down with the additional quantity (up to a point), and it is in general more interesting. Also if you use for instance AliExpress shipping or Chinese Post, you can reduce slightly the shipping if you buy few or several goods from the same vendor instead of buying the "best" price from different vendors. It is not written, you need to perform a check with both the quantity and the mode of shipping.
For instance I bought recently several small electronic cards, LCD, SDCard readers... for prototyping some hardware from the same vendor using AliExpress shipping, I bought for 40 $ of goods and the shipping went from 33 $ to less than 3 $, as you can see it is a huge difference from a price and also shipping with tracking safety in case of issue.
As a rule of thumb, it is not worth to buy anything big or heavy. In such case, you need to check on Ebay if a Chinese company is big enough to provide the good you are interesting into through a "satellite" company not far away from your country. For instance I bought my Wantai stepper motors from a Wantai "satellite" company in Hamburg, Germany.

Daily price variation

From day to day you can have a better deal, it is always worth to check and recheck a few days before buying.

Personally, I like a lot AliExpress it is another world and there are a lot of interesting goods.

I hope those small tips are useful, if you have others I would be interested :)