Today, without the help of an external counsel, you cannot run an in-house legal team. 

In litigation it is essential and in advisory it is preferable.    

Choosing of a counsel is a tricky affair.

A wrong choice may take you for a toss and you may be sandwiched between the top management and the counsel.

In my view, at least, you should consider the following aspects before the appointment. 

1. Policy

Check whether internal standard operating procedures (SOP) / policy guidelines are available for such appointments. If yes, adhere to it. Take a prior approval for an exclusion, if it is an exceptional case. This would ease the payment processes;

2. Experience

Gather the experience and expertise of the counsel vis-a-vis your case in hand; You can't choose an IPR lawyer for a real estate due diligence! Ensure that the counsel's office doesn't have a "Conflict of Interest"

3. Availability

You can't afford a counsel who is stuck up in another meeting while you are at his/her chamber for a pre-decided conference; you can't either tolerate a counsel who doesn't pick up your call or forget to give you a return call

4. Confidentiality

Confirm that the data you are going to share with counsel would remain confidential; (I was told that a client has changed her lawyer because the counsel did not have a private email - he was using a public domain email)

5. Counsel's office

Ensure that the counsel has an office with all required facilities (communication, meeting, fax, scan etc.,) Don't run for a photo copy to the next shop at the neck of a moment...