I found it really hard to know what good meant too!
If you have been in an abusive relationship, Women's Aid will be able to recommend a solicitor who is experienced in "coercive control". Otherwise, I found they were (probably) similar in terms of the advice they gave, some just got it across better than others.
So for me good meant not so much what they said, but how they said it and whether or not your meetings were followed up promptly with an accurate written account of what was said, whether phone calls were acknowledged with an email response... there needs to be a good and clear paper trail.
You don't want to be sitting around waiting for call backs and letters.
Also, my solicitor filled in all the forms (which costs but no time gets wasted because you made a mistake, etc)
Also, instinct. You need to "like" this person or at least know they're on your side and will be fair.
Hope that is of some help. Good luck!