Arbok is not going to single-handedly win you many battles. What it can do is throw your opponent off of his or her game sometimes and, with a little luck, endlessly damage your adversary. While Arbok has decent Attack, its HP and Speed are mediocre, and its Defense and Special are bad. It can't so much function as a physical sweeper as it can as a support (and aggravation) Pokemon.
Arbok can really only be used well in the UU environment, but should it stray, the likes of Starmie, Alakazam, Golem, Rhydon, and Exeggutor will eat it for lunch (well, at least Arbok can potentially paralyze the last three before dying). Its defenses are really poor, and even if it is hit by something that isn't super effective, it will bite the dust fairly quickly.
You can start off by using Glare, but ideally you will have slept and paralyzed parts of your opponent's team already. Arbok, barring critical hits, is going to do about 3% damage each turn with Wrap, so it is going to take a long time to get anything into a low enough HP range to be KOed by Hyper Beam or Earthquake. As neither move receives STAB, Arbok will never do much more than 30% with Hyper Beam and probably not much more than 40-50% with Earthquake if it's super effective. Your opponent is also likely to keep switching between Pokemon in an attempt to make Arbok miss, and it will be locked into Wrap until it misses while they do this. Arbok is pretty fast for a UU Pokemon, so if it misses on a Pokemon that is not faster, such as Tangela, it can fairly safely Wrap again. You are going to need to get most things to lower than 30% to KO with Hyper Beam, so if Arbok misses on something faster, you should switch and not risk losing it. You can use Arbok to your advantage to switch in another Pokemon if turn after turn they do not switch out, because they will not be able to attack if Arbok's Wrap would have continued. Using this opportunity to switch in a sweeper is a great idea. If they are repeatedly switching between just two Pokemon, you can once again switch to your advantage. Arbok does not have much in the way of STAB, although Poison would only really hurt Bug- and Grass-types, and most UU Grass-types and some Bug-types are part Poison anyway. Hopefully it will not matter, as Wrap should provide Arbok with all the offense it needs!
Body Slam can provide damage and a chance at paralysis with higher accuracy, if you don't want to use Glare. Mega Drain can hurt Rock- and Ground-types, although Earthquake does so as well, and Arbok has a low Special stat. Rock Slide is an overall decent move, and Screech can force extra switches. Arbok can use Fissure if OHKO moves aren't banned, although enough Pokemon still outspeed it in RBY to make this risky. It can learn Acid for STAB, but it's not really worth it.
Checks and Counters
If, for some reason, you're using Arbok in OU, Rhydon and Golem are counters if it doesn't have Mega Drain. Alakazam, Exeggutor, Slowbro, or just about anything that gets a STAB Psychic will put quite a dent into Arbok. Snorlax, Zapdos, Articuno, and Moltres can all counter Arbok regardless of the set as well, as they all will hit Arbok hard and can take hits from any Arbok set.
Chances are that you are using it solely in UU, where Omastar and Kabutops are good counters, again provided it isn't running Mega Drain. Both of them do not fear its non-STAB Earthquake too much, and fear Wrap even less thanks to their part Rock typing. Electabuzz and Arcanine are both faster than Arbok and they have higher Special stats with high-powered moves to hit Arbok with, but they need to be wary of Earthquake. Aerodactyl does not fear Wrap or Earthquake in the least, so if it is not paralyzed, it will perfectly counter Arbok. Dugtrio is also a fearsome counter, having huge Speed and STAB Earthquake.