What should be the order of references in a research text? In many research articles numerical values are used for citing references in the text. I have seen the numbering of such references in pretty weird orders.
In some texts, the references are sequenced as they are cited in the article. For example, 

Case 1:


  Statement X[1], says that the technique ABC[2] solves the problem by utilizing the Y method[3]


While in a few, they seem to follow random ordering like

Case 2:


  Technique X[95,46,38] has been long used for solving the problem
  discussed in [12]


In some others

Case 3:


  Technique X[56] has been used in [23] to solve Y.


Are there any standard conventions or best practice for ordering the references ?

(My field is computer science)
The order is determined by the standard applied by each journal to their publication. In some cases, references are listed alphabetically in the reference list. In this case, the order of appearance of the numbers in the text may seem random (this is equivalent to your cases 2 and 3). In some cases, references are listed in the order they appear in the text. This yields the first example you provide.

So there is no right or wrong, there are different standards and which you need to follow is given by the journal in which you aim to publish.If you are concerned with which system to use in a report or your thesis, you should simply check with your department or organization to see which they follow. If there are no guidelines, I would suggest the system you find most commonly used in journals that lie close to your subject but you could essentially select whichever one you want as long as it is consistent and logical.