Ebay and Poshmark are improving by the minute and with that, the necessity to not only constantly educate but re-invent yourself.
I do that thru tutorial videos from other sellers, reading articles about the companies but, mostly, from trial and error. Every seller has a specific business model. Some buy cheap, sell cheap. Some concentrate on a specific niche where takes longer to sell their products, you name it...
For me, Ebay is about posting new items daily and you will get sells. Poshmark is about being social with whatever you have posted. Both of them require time and dedication. There are not an instant gratification kinda venture.
What have I learned this week?
Ebay: offer sales. Daily. If you have a store you can decide which category/ies you want to mark down for 1 day, or 2 or for the entire weekend. Don't overprice and then run the sale. Buyers are smart :)
Poshmark: take advantage of the shipping promotions Poshmark offers when available and run a discount with it. The combination is a BIG motivation for buyers.
Bonus track: cross-post. You NEVER know :)