Ok, there are a few things going on here.
First, I see you are at the beginning of your studies, so it’s natural that you see the ます form and try to grasp things from it. But I promise you if you keep studying just for a while more, the ます form will quickly stop being the default way things are presented, so it will be pretty obvious if a verb is さ行五段 (話す) or a する verb, to the point you will never really wonder about that again.
That being said, I understand that even being told that, you probably still want something you can do for now (at least I would.)
So the gist is understanding what a する verb is. It is necessarily a word + する, so there are a few strategies you can think.
・If a 熟語 (two kanji making a word) comes before the します, it is most likely a する verb, like your 勉強します, 掃除します, 料理します, 結婚します, etc.
・If there is a hiragana between the kanji and the します, it is pretty guaranteed to be a す verb, 欠かします, 鳴らします, 飛ばします, 落とします.
However, there are still the one kanji + します verbs. At the beginning most of time they will be す verbs (話します、出します、回します、倒します), but as time passes you will start seeing some that are indeed する verbs. So if you can’t check it, just guess for す, but don’t take it for granted. The actually common one I can come up with is 訳します, but as you advance you might see 対します、面します and others, but it is really hard to see them in the end of a sentence, so it shouldn’t be a problem.