renting in a mall - what makes you decide yes/no?

i lowered my prices to $200/60 prims and $150/40 prims

so, now i need to figure out how to 'open it up' without exposing the ugly ad farm behind it, and giving up space for my park. hmmmmmm

Sorry Novis, it means "full".

If there's a large number of banned av's in the list, it's a good indication that either griefing occurs frequently or the owners have made a lot of enemies.

A perfectly built mall with all the traffic in the world still can't sell "everything".

Adjacent locations are not very important, because most people will just TP. Traffic can be valuable, but it's worth checking the parcel boundary lines quite carefully. Some mall owners will "gerrymander" by, for example, placing the mall on the same parcel as an enclosed club, so that all the people staying and dancing in the club count towards traffic for the mall. Of course the vast majority of those clubbers never go to the mall and the traffic is meaningless.

The artistic quality of the build is sort of important but not critical - while it might have some effect on walk-through trade, it's unlikely someone will leave somewhere that has a product they want because it isn't an attractive place. (Oh, and if it is an attractive build, and is very new, remember to subtract the traffic the builder generated while building it!) What is important is shop placement - some malls are build with obvious "top spots" and "bottom spots". Obviously it's worth avoiding the "bottom spots" but it may also be worth avoiding the entire mall - because why would they have deliberately built bottom spots? (Beware of themed gimmicks like "secret shops" by the way. They're well-marketed bottom spots.)

It's good if there are other people in the mall, but of course it's a tradeoff, because those other people will have taken the best slots if they're already there when you get there. If you find a mall where the best spots are taken by "big names", or they have outsize stores.. then it may be worth surreptitiously asking around a little bit to try to find out what rent they're paying. Some mall owners will give the big names slots for nothing to make the mall look better. You might think they'd generate walk-through trade - and real life malls give 'big names' cheap rent for exactly that reason - but in my experience it doesn't work that way in SL. The bigger someone's name, the more likely someone searching for their product is to teleport to their main store, not to a mall. The only reason they have stores in malls is to make people notice them, just like every other business.

I chose not to rent a spot in a mall because i built my own mall.

As Ciaran mentioned, that direct TP to the storefront is critical (and answers a comment by Nina, I think). Also mentioned by others is the lag profile of the sim, especially texture download time.

One other thing worth considering is the demographics of walk-by traffic. Pretty much everybody measures the SL "age" of shoppers, but mall owners rarely share this info. It's important because for traffic to be meaningful to sales, it kinda has to match the market for the products a shop has on offer. That is, if one is selling n00b-priced items, a mall full of upscale products probably won't attract the right traffic--and possibly worse in the opposite situation.

Further to this point: Surroundings beyond the mall itself can matter for different demographics, too. While the vast majority of Mall shopping traffic comes from Search, at least a few visitors will stop by after a trip to a park or other nearby attraction. (Perhaps a more obvious example: gay-themed products near a gay dance club.) If the surroundings match the shop's target market, it can be a plus.

I have recently set up a new mall with about 40 shops. It is on PG Mainland and my rents are based on $L5/prim. After friends and neighbors set up things they had to sell, I set about getting more renters.
I have found that the direct IM to vendors can be a good thing or a bad thing. I go around established malls, most where I already have shops (I sell my own jewelery) and compose a personal message inviting other tenants to rent at my mall. I have sent about 2 dozen messages and gained 4 new renters over the last week. I have actually made new some friends by continuing the conversation with them once they respond to the invitation. (It helps to heap compliments on their work) On the other hand, there are content creators who view these messages as bad spam and actually have info in their profiles warning people not to send them any f%#*g invitations to new malls or they will hate you forever or some such. These are usually old-timers who have quality merchandise and I suppose they have no need for additional outlets. I skip them, as I do those with low-quality or questionable merchandise.
Nonetheless, the direct IM to potential renters seems to be a strong tool for contacting these people and giving them a slurl to the place so they can check it out.