Valid modes used in the contest should be called out explicitly in the rules.
Dupe example: "Work stations on 3 modes per band: PH, CW and Digital (all non-CW)".
Multiplier example: "Multipliers are counties per mode: PH, CW and Digital".
Most sponsors use `RY` for all non-CW digital modes. Ex: "All non-CW digital modes are `RY` in Cabrillo".
It is very important to make modes clear in multi-mode digital contests, otherwise there will be duping issues and NILs in cross checking. Dual mode contest example: "Work stations on RTTY and PSK63 on each band. RTTY is `RY` and PSK is `PK` in Cabrillo".
Mults must be detailed in the rules as well. "Multipliers are States, Canadian Provinces and DXCC countries" is so generic that software authors will scratch their heads. If the rules are explicit, then chances are that more submitted logs will be formatted the way you want them.
Ex: "Multipliers are US States (50), Canadian Provinces (14) and DXCC countries, once per log. US, Canada, KL7 and KH6 do not also count as DXCC multipliers. Canadian Province mults are: AB Alberta (VE6), BC British Columbia (VE7), LB - Labrador (VO2), MB - Manitoba (VE4), NB New Brunswick (VE1, 9), NF Newfoundland (VO1), NS - Nova Scotia (VE1), NT - Northwest Territories (VE8), NU - Nunavut (VYĜ), ON Ontario (VE3), PE - Prince Edward Island (VY2), QC - Quebec (VE2), SK - Saskatchewan (VE5) and YT - Yukon Territory (VY1)".
The Canadian mults and abbreviations could be listed as a separate appendix. The same with the US state abbreviations.
Details about log format, classification and submission will increase the chances that logs are the way you want them. If the log submission format is Cabrillo, be specific about the format by publishing a Cabrillo template so logging software authors can write the correct output file.