Set for all products
Perhaps the most basic rule, but because of its usefulness a very common one. If a field needs to have the same value for all of your products, simply create a rule that sets these. Using 'and' statements, you can do several of these in one product.
Remove products that are out of stock
Don't want to send a certain group of products to a channel? Simply add a rule that removes these products. Common uses are for removing products that have poor margins or are out of stock.
Free shipping above price X
If the data you imported does not have any shipping price in it but the export channel does require it, you can use rules to add this information. An example would be if you provided free shipping from €100. In this case you would actually have two rules: one for setting the regular price (see 'Set for all products') and one for products that have a price that is greater than 100. Do keep in mind that rules are applied in order from top to bottom, so make sure that you first set the regular price for all products before setting the discounted price for a subset of your products.
Add a phrase to a title
Using the 'append value' operator, you can add any word or phrase to a field such as your title. You can use this to add phrases like 'Sale' or short information about your business.
Mix and match!
Rules are extremely flexible, almost anything can be done using them. You can combine these examples any way you like.