there really are no magic tips. the only thing you can do is (yes the love letter) and try to clean up the terms - short inspection and loan contingencies. have strong relationship with their lender and see if the lender would be willing, if necessary to talk with the listing agent to address any concerns the listing agent has regarding financing.
i have a new listing that needed some sprucing - i went to target and bought some things (which I will return) to tart up the bathrooms, kitchen and living room - plants, kitchen stuff, towels, pillows for the couch, etc... At Compass we have a concierge service that allows the seller to borrow money interest free to renovate, stage etc...or just do a deep clean and leave the house as clean and empty as possible and the buyers use their imagination.
ultimately, developing relationships with other agents goes a long ways. i've gotten many deals done bc i had a long history with the listing agent. obviously this takes many years to develop - but something to shoot for.
i hope this helps!
best, Solo