I am Kanishk Singh, engaged in selling Magnesium Citrate Anhydrous in Russia, thus, it is extremely important for me to select a reliable supplier of Magnesium Citrate Anhydrous.
Google “Company Name”
A renowned company name usually shows a great deal results on Goolge Search, because its company name is frequently searched by their customers or cited by other web sites.
Take “Foodchem International Corporation” as an example, as has been showed in the below picture, there comes out more than 298,000 searching results on Google. 
Warehouse
Warehouse is also important for Magnesium Citrate Anhydrous suppliers, Magnesium Citrate Anhydrous traders make judgments through Magnesium Citrate Anhydrous market situation. On one hand, while Magnesium Citrate Anhydrous is in the upside, traders purchase bulk Magnesium Citrate Anhydrous for storage, and sell with the price advantage; On the other, vendors need to keep cargo in warehouse in case customers need LCL loaded.
Foodchem International Corporation owns an EDC warehouse in Shanghai, an advanced warehouse system which only few trading companies in Shanghai can provide, it avails fast delivery within 1 week.
Company Name
As a professional trader or manufacturer of food additives, normally its company name has food, chemical, additives or other key words in it. Other trading companies who have affairs in all fields, usually performs unprofessionally.
Sales of Supplier
There are tons of suppliers of Magnesium Citrate Anhydrous in China, thus, supply scale should be important, Magnesium Citrate Anhydrous suppliers with a certain size suppliers tend to have more bargaining power, in some country, we can even find their Magnesium Citrate Anhydrous supply volumes through customs data.
Location
Generally cargo takes ship delivery; thus, sustainable trading companies tend to set their sites in coast cities, such as Shanghai, Qingdao, and Tianjin in China.
Supply of Products
Compared with Manufacturers, other than service advantage, main advantage of trading companies lies in being able to provide various kinds of products. For example, when we would like to order Magnesium Citrate Anhydrous as well as several other food ingredients, trading companies becomes the best choice, since unlike factories, traders can provide one-stop service and have greater bargaining powder which permits a lower price.
Of course , we can purchase Magnesium Citrate Anhydrous directly from manufacturers if the volume is large enough, but it won’t be a bad choice if we keep in touch with some large-scaled traders. Because once your long-term-cooperate factory is in short of Magnesium Citrate Anhydrous , we can turn to trading companies, who can help to find other suppliers shortly or even direct supply Magnesium Citrate Anhydrous in no time.
As far as we know, big suppliers of food additives and ingredients can basically provide more than 100 kinds of products, among which, Foodchem International Corporation are able to supply overseas customers more than 300 kinds of food additives and ingredients, plant extracts, nutritional supplements, apis, etc.
Certificate
A formal operation supplier of food additives normally passes ISO certificate as well as other well-known certificate like halal, kosher, ect.
http://www.foodchemadditives.com/products/Magnesium-Citrate-Anhydrous