I often ssh into my machine, and then run 'screen -r' to connect to my (usually) running screen instance and pick up where i left off.
However, i feel it's tedious.
My question is, where (like, .bashrc or wherever else) could I put a script to first check for a running screen instance; then if one exists, connect to it.
I'm ok with building the script, I just don't know where to put it.

It's rather easy:

The -t is needed to force the pseudo-terminal allocation needed for an interactive shell.

If you are trying to attach to a specific screen session then include the -S option.

Edit: be sure to see the RemoteCommand and the RequestTTY directives for ssh_config.

The existence and use of ~/.ssh/config might be a little obscure so here is an example of what can go in it:

That will allow you to connect just by typing "ssh sss1" and nothing more, all the settings will be made automatically based on that shortcut.

The full set of configuration directives can be found in "man ssh_config". Note the lack of a "d" there. Most run-time arguments have corresponding configuration directives. The client goes on a first-match basis so the Host patterns must have the more host-specific settings first and the most general settings last.

My guess would be to call it from .bashrc, if you want it to run every time you login...as when you su - to that user from a running session...but what do I know?

An alternative I use is to write the script with a name I can invoke with a couple of keystrokes by invoking the history.
For example: I have a script that scans my spamtraps named ckspam.sh. After login, I type !ck to invoke the script. Most of the time, it's also the last command I've used on a session, so up-arrow, enter will also re-execute. The latter probably wouldn't apply in your case, but if you had a unique-enough script name (sz.sh) you could invoke it with !sz anytime you wanted.