What are the odds of getting infantry through my commission as an officer?

Coming from someone just recently commissioned IN through ROTC, you need to focus on the following over the next 3-4 years: Highest GPA possible, Campus OML points(earn these through leadership rolesat your BN and assessments from your cadre), 300 APFT(should be a given considering your goal), doing your best at Advanced Camp( strive for top block rating), and finally paint the picture for ROTC talent management. Show them through your time in ROTC why you fit the model for a potential IN leader, this is a large aspect they’ve implemented in the last 3 years which helps cadets throughout the National OML land in the right branch regardless of FY ranking. All of these come together to give you your ranking on the National OML and th snapshot the accessions committee will use to branch you based off needs of the army.

Depends odds are good if you are high on the OML and can get first dibs on the Branch you want

Yes, the order of Merit list and a 300 on your APFT will help. When I used to get a 300 on my APFT, life became easier as an officer. Had I not broken my ankle, I would have been able to complete Airborne School in civil affairs. I was the top of the order of the Merit list due to my PT score. Like others have said here to network with the local infantry battalions near you and talk to their Battalion Commanders. It's helped me when I wanted to switch from military police to armored to just call up armored unit and the Battalion Commander interviewed me over the phone and next thing you know, I was transferred to an armored unit. When he introduced me, he mentioned "here is 300 APFT Lieutenant Conway!" That was just my personal experience. When I was about to be commissioned in the California Army National Guard, the guard was smart enough to have a job fair for the OCS class. I ran and got one of the few military police slots there were. All of the advice from others here is valid.