If you are not yet on LOTW, here is a helpful link on how to setup and use it: g4ifb.com/LoTW_New_User_Guide.pdf
For domestic (USA only) QSL cards a SASE (Self Addressed Self Stamped Envelope) is appreciated for domestic contacts. I enjoy getting them and will respond as quickly as I can. I get several a week so please be patient.
For international requests (outside the USA) you can do a ClubLog OQRS or Green stamps (US Dollars) to my address is fine. CAD, EURO or your local currency is also fine if USD is an issue. I travel a lot, so I can always use it.
I log ALL QSOs not just HF. This is including those via Satellite and VHF/UHF/SHF. I especially appreciate cards for 6m and above as well as for satellite/EME contacts.
In addition to physical cards, I also QSL via LOTW (My preference), eQSL or via the ARRL Bureau (ARRL 6th District) but it might take some time. These get shipped about twice a year. I also Upload to QRZ , HRDLog and ClubLog when I get a chance or about once a month.