The following relevant points (not necessarily arranged in sequence) may be considered :
These points were done just off hand. For a proper article ,there needs to be a lot of additions required - specially Holy verses and Holy traditions. Lot of analysis and situations need to be discussed. Making such a document may need time that is difficult to get presently.:-

1. There is ultimately a common man behind any Alim. You can first apply the general rules that are applicable to know the integrity of a common man to an Alim. Lots of general rules apply.

2. You do not make ultimate decisions related to any person including an Alim. Personalities change. When Allah (S.W.T.) has provided him time till death then you are no one to find an alternate to this rule. But don't allow any person to affect the interests of Shias.

3. When there is any wrong action you need to do Amr bil Maarof and Nahi anil Munkar irrespective of the person involved is a common man or an Alim.

4. Besides Abm/Nam there is also a very important aspect to be noted - defense of Shias. Whether there is a common man or an Alim working against the interests of any/all shias you need to stand in front of him. This is truer related to an Alim than a common man and you need to be more observant in this case when looking at an Alim.

5. You need to learn more about the prescribed law in Islam. Judge the person according to his actions. If you find them to be in accordance with the law then he is a good person or Alim and if you do not find them to be in accordance to law then it can be specifically at least said about the Alim in most of the case that he is not genuine.

6. Don't form opinions about anyone based on the opinions of those who themselves do not know and understand the Islamic law.

7. You will find a good Alim always giving preference to the work of Shias to his personal needs. This may be to an extent that whatever he tries to gather for himself, he has plans to ultimately benefit the shias. This may be difficult to know but not impossible when you have an interaction with the Alim.

8. You cannot always react to personalities. You need to react to apparent actions that have been performed or is presently being performed / apparently planned to be performed.

9. In many cases you cannot degrade a person to know about him.

10. You cannot rely on any person 100%. You need to have certain checkpoints always in place.

11. When you interact with an Alim you find yourself closer to Allah (S.W.T.).

12. The Alim relates himself to Allah (S.W.T.) and the holy AhlulBayt(A.S.) more often.

13. Love of Allah (S.W.T.) and the Holy AhlulBayt (A.S.) shine from his forehead.

14. The Alim has emotional feelings for the Law of Allah (S.W.T.).

15. A good Alim will not leave you because you offend/ cause loss to him if there is a purpose of Allah (S.W.T.) associated with you. An Alim will not associate very closely with you even if you favor him with appreciation and otherwise if there is no purpose of Allah (S.W.T.) in it.

16. After all the necessary/ religiously possible ways even if you rely on an Alim, you should always ultimately rely on Allah (S.W.T.). An alim can desert you but the base on which this reliance was standing, that is relying on Allah (S.W.T.) will always stand by you and your purpose.

17. Duas are useful for anything and everything. You can sincerely ask Allah (S.W.T.) for guidance related to this matter as well.

18. Ultimately, be lenient with others and firm with your own self if there is no associated risk for the shias or any aspect of Abm/Nam. This will help you in this life and the hereafter.

19.A genuine Alim may make genuine mistakes. If an Alim happens to commit a mistake it does not mean that he is not genuine. But when he realizes it or when he is reminded about it then he accepts the mistake and rectifies.
There are many more points on this topic and also complex situations involved in these points. But in general, these may help

When we say "no associated risk for the shias " & "But don't allow any person to affect the interests of Shias " ,"working against the interests of any/all shias" it implies that we are supposed to judge this ourselves through our own common intellect and using the shariat as the benchmark. We cannot rely on any Alim for this. We should listen to the reasonings of an Alim and then deduce ourselves. Inputs are from others, using our intellect with the benchmark of shariat is from our own selves.
Also, you are supposed to do taqleed in getting the theory (Islamic Laws - Hukm) and not deciding the subject matter (mauzoo) in implementing them.