
Matthew S. answered 07/14/19
Certified Teacher with a Specialty in High School Math
Well, first of all, one thing you can do is a variant of leaving out the speaker's name where you use the "he said/she said" tags only every couple of sentences. Basically, you use those tags at the beginning of the scene for the first line from each character, then leave the tags out for a few lines, mention one person's tag, wait a few more, etc.
Making sure your characters sound distinct is also a good idea, but you don't have accents or difference in vocabulary to pull it off, although that does work. It all comes down to the type of character they are and the kinds of things they would say. For instance, if you have a grizzled, seen it all cop who just wants to find the murderer so he can go drink himself stupid back home and a distaste for polite society, he's unlikely to be the one saying "Aw, look at the cute puppy!" You can also do things like have quiet or focused characters use shorter sentences than boisterous and excited ones, or have a formal character use full words rather than the contractions and slang their laid-back friend uses.
Another trick is to use context clues based on what is happening to the characters. For instance, if Mark and Susan are talking to each other and one of the characters says "Ever since you got pregnant you've been nothing but a pain", you can probably guess that Mark is speaking even without a tag.
One of the most important things you can do though is let us know what the characters are doing. Rather than use tags, you can tell us what the character is doing while they're speaking. For instance:
"Aw, look at the cute puppy." He rolled his eyes before continuing his glare. "Makes me wanna puke."
You can even combine this with the other ideas, such as using these in conjunction with rare "s/he said" tags. To use your example:
I found an important clue," Bob said.
"What was that?"
He handed Sally the photo he'd taken at the crime scene. "The killer left behind a glove."
"Perhaps we can identify him from fingerprints or DNA," she said, smiling.
With this, you can use half the tags or even less while always making it clear not only who is speaking but what they are doing. These and the other tools should give you enough options to make your dialogue feel varied and a natural part of the scene.