First, a lot of people wind up in graduate schools that are rated better/higher than their undergraduate institutions. It can have some impact, but is normally not determinative. Of course, it is harder to get in to "top" universities than others since the competition is much stronger, but it is still possible if your application materials clearly indicate that you are a good candidate for success.
Anything that can make success seem more likely is a help. Publications, certainly. Research, even if not completed is a positive. Good grades, good letters from your professors, all contribute to a larger picture.
If any of your professors studied in the places you are contemplating, you might ask them for advice. Sometimes the personal contacts between professors can have an effect, depending on the admissions system. At a minimum, a letter from someone trusted by the reader has more impact than it would if there was no such relationship.
Make sure your CV is complete and, very important, make sure that your SoP talks about your future career goals and how you intend to pursue them. Any ideas you have about research projects can help, though less detail is probably a good thing. If you aren't a native speaker of the language of the country you apply to, make sure your materials are checked by someone who is so that the language is correct and not misleading or awkward.
And, also very important, is to apply to a range of institutions, not all rated about the same. There are a lot of good universities out there that aren't rated near the top in their respective regions.
