I choose airlines that don't have a lame carry on weight limit then go from there. BA tend to be very good for that,but the easiest way to find out things like this and other useful info is to go to Seat Guru.
Here's the page for BA's luggage for example
, which has a size but not a weight limit for carry-on. Virgin Atlantic a big rival of theirs was a paltry 6 or7 kgs.
Other things to be careful of are flights with connections as it may be a different airline for part of journey and with different rules. But if entire ticket is booked via BA for example then BA's rules should apply - but do check first.
Other ways of getting under restrictive weight limits are if you can carry laptop/cables as a separate bag. Some flights allow a second bag like handbag/laptop others do not. Also avoid going via the UK if you can to avoid having to deal with the jobsworthies at the airports here.
[For non-Brits, a jobsworthy
is someone who insists you place your camera bag in the hold because it's 50g over the 12kg weight limit and justify this by saying 'it's more than my job's worth to do otherwise'