Then you need to consider what depth to defend at, cover 1 has 1 deep safety and puts more players closer to the line, cover 2 has 2 deep safeties and generally plays a little further back, cover 3 has 3 deep etc and protects even further back etc.
If they come out with 3 or more receivers you want to be in a nickel defence at least. If they come out in a run package (HB/FB, multiple TE etc) then your base stating point would usually be a 4-3 or 3-4 defence. Generally you should match up what the offence does. Are opposition receivers getting open deep or underneath? Does the QB have a long time to pick a pass? etc. On defence you didn't give a lot of information as to what you are doing. Practice being able to make adjustments quicky pre-snap until they become second nature.
You can also adjust a receivers route on the pre-snap if you are able to spot something you can take advantage of. Once you're getting it right more often than not, adjust your audibles to include plays designed to take advantage of different coverages so you can exploit man or zone, or cover 1, 2 or 3. It's not 100% guaranteed as some defences are designed to mask the actual coverage until the last second and then you often need to read the movement of the safeties to figure out what the defence is doing. I would suggest looking up guides to help you be able to read defences.
