I fly out and back almost every week.. or at least a few times per month. Unlike the new D and renovated E construction that plagued IAH for what seems like 5 years, the current B renovation/rebuild is funded by United, not public/government contracting, so allegedly it should only take about a year instead of 5... or so I'm told. but alas, the traffic will continue in and out of IAH for a while.
As per usual, if you want to park at terminal C/E and you're not leaving early on a Monday morning, terminal parking will be pretty full if not completely full (like later Monday or on a Tuesday morning), so if you don't want to take a chance circling around looking for a spot, you can enter C/E and try to cut across to the old purple garage where there are usually spots.
Otherwise, your other options are
1. reserve a spot- I prefer valet- at least 12 hours in advance. You won't be able to pre-book terminal parking the day of travel, but if you remember the day before, book valet and save the hassle.
2. park at A and take the interterminal tram. If you're not checking baggage, you can use A's short security line and use the fast and frequent above ground tram to B, C, or D/E. If you're flying United or international out of B/C/D/E and trying to enter in terminal A with oversized checked bags, you'll have to take the under ground tram, but that thing is slow and runs infrequently if at all so I'd recommend against this option if you need to check bags. Also, both trams stop running at night- early like 8pm for the above ground one, later for the underground one- so beware of what time you return and have to find your way back to A where you parked.
3. Uber/Lyft to IAH. Could be cheaper or a wash depending on distance and timing/surge pricing. Convenient getting there; can suck when you get back, especially the madhouse zoo of the C ride share pick up zone. A recent Uber driver told me a hack - to go to the E pick up zone no matter what - shorter, easier in and out, and the divers prefer it- but you can't do that if you checked bags and have to go to C baggage claim.
4. park offsite at one of the two ecoparks or one of the two sparking spots and take the shuttle bus. This can also suck waiting for a bus that isn't completely full when you return, depending on day/time when you get back, especially from C baggage claim. If you didn't check bags, consider tramming to A and catching an ecopark or ecopark2 bus there in stead.