@Fryguy1111, an important consideration is using not only stranded wire (which is true for
all DC power) but specifically marine-grade stranded wire, which is tinned copper - each copper strand has been tinned so that the copper doesn't basically instantly start corroding in the moist and salty conditions found in marine environments. Ditto for your crimp lugs, you don't just want copper, you want tinned copper lugs. For your solar wiring, same deal, you want to use tinned copper cables everywhere possible. The wires that come with your panels won't typically be tinned copper, but you want everything from there back to be the proper cable.
Otherwise, of course you want everything you're using to be marine-grade and to have ABYC certification. For your battery switches/breakers you want the Blue Sea/Bussman battery switches (like the 9003e for a simple on/off switch, though there are lots of other options) and the Blue Sea/Bussman OEM 187-series surface- or panel-mount breakers are marine rated and freaking awesome little switches. There are also the MRBFs (marine-rated-battery-fuse) which are fuses that mount in a little holder directly onto your battery M8 posts or threaded inserts and you then takeoff your power leads from there... very good in tight areas where you might not have room to mount a full ANL fuseholder or such.
For your shrink tubing you really want to use 3-1 adhesive-lined shrink tubing to ensure that you get full sealing when you shrink it down.
Per ABYC, any busbars or fuseholders that you have of course need to have covers on them.
Any electrical devices like inverters or solar controllers should have an IP rating or at least drip-resistance when mounted in particular orientations, and anything going in an engine room needs to be ignition-protected...
...lots and lots more things like that; your inquiry is a bit broad to be able to address in total, so if you have specific questions, feel free to post them here and I'll answer what I can. ABYC regs and marine applications for power generation/distribution components are a large part of our business (roughly 40%), so we stock pretty much everything a boater might need to generate/distribute power and we know pretty much everything about what we stock, so there's a good chance that I -if not indeed several other members of this forum- might be able to help you with specific questions. Maybe start with a rough description of what you have vs. what you want to do?