Idliver-SCGREA
Here are a few suggestions:
1-www.njactb.org website. Go to legal archive and download NJ Assessor's Handbook. It outlines the appeal process with guidelines on evidence.
2-If the appeal is at the commission level a gpar form is fine. If it escalates to tax court, a narrative is recommended.
3-Have back-up and documentation for your adjustment "opinions", ie: Marshall & Swift or contractor estimates. May not be a problem at the commission level, but tax court judges want the "Whys and Wherefores" of your professional opinion. (See Greenblatt vs Englewood)
4-Remember to equalize the true value of the assessment to be sure your value conclusion is "outside the corridor". Otherwise, you're wasting every ones time.
5-Don't cherry pick your data. If your comps are well researched, in the neighborhood, similar style houses, and with similar amenities, and if you have a legitimate case, most assessors will be reasonable and offer you a settlement. If you cherry pick the low comps and advocate for your client/friend, instead of employing appraiser impartiality, the assessor will respond in kind.
6-Don't forget to re-equalize your value conclusion back to the current ratio and calculate the potential savings in a best case scenario. In my experience, you can expect a fair assessor to negotiate toward the half way point, maybe a little more than halfway. If the savings is not significant, don't spend the time.
Good Luck