How hard: it depends how big you are and how much you know about your customers. For a large multiple, a huge amount of science goes into developing deals for their shoppers. They try to deliver promotions that are timely and targeted. They have complex buying, marketing and merchandising operations to keep synchronised.
For a local shop, you can see the customer you want to focus on and you can ask them what they are looking for. Next you can source the deal and then deliver it on time in your one location.
However, if you want to maximise the investment of suppliers in your promotion, then you need to impose greater discipline. If you want to earn overrider payments, you have to take promotions designed for the average shopper, not your own customers.
If you choose to step up a level, then you need to improve your own disciplines. The first thing you need to do is tell yourself that you will have regular promotions. Perhaps 13 times a year, perhaps more. Some could be obvious (Christmas), some could be opportune (a local festival), some could be things that you are passionate about (a charitable cause).
After setting your timetable, you then need to consider what success looks like for each promotion. You need to know what will make them worthwhile: more customers, more sales, more profit, new ranges, new services etc.
Once this is in place, then you will start to think about planning ahead so you can make the most of the opportunity. If you want support, then you need to keep track of previous results, to give partners confidence. From this you will find out what type of merchandising works for your shoppers and what kind of deals.
Armed with this knowledge you will be talking to your suppliers about how they can design promotions that will work for your customers. This is where it may get interesting as they will find that getting a good deal in front of your shoppers will demand the sort of attention to detail that the major multiples need to make.
Its may sound like a long road but it should be worthwhile to travel it.