There isn't really a way to tell, you just have to love what you get! However, if the two dogs have littered before you can ask what the outcome for ears was and that can indicate what you are likely to get!
Just a week ago my 3 mth old morkie's ears started to stand up. When we got her her ears fell flat. She changed in just a week, so not really sure there is a way to tell if the ears will stick up. It's really cute though!!