Starting out with Terrans

Terrans
It's not really recommended that Terrans rush with Marines. Against Zerg,
hordes of Zerglings can overwhelm Marines at close range, while Zealots
can of course, tear through infantry with ease if the infantry force doesn't
have a large advantage in numbers. Marines fare much better in Bunkers,
so playing a defensive style at the outset would probably be the wisest
course of action. Advanced players might shun this advice and try using
the Marine Rush strategy but that entails risks which new to intermediate
players may not be inclined to take.

Offensive Bunkering
There are a couple exceptions besides the Marine rush. If the other player
is a somewhat slow builder and within close proximity, it may be possible
to get your first two or three Marines to his town to kill worker units. Once
that happens, constantly streaming in troops will probably wear down and
defeat your crippled opponent. Another possibility to consider is building
Bunkers/Barracks right outside your opponent's base and staging attacks
from there. It is somewhat risky, but if you use 2-3 SCVs to build several
Bunkers simultaneously (and later use them to repair the Bunkers as they
come under attack), it can work against unwary opponents. Of course,
such a tactic would work best against a player who is not rushing himself.
Early recon of your opponent's structures can help you determine what
strategy he/she is using.

The important thing to remember is to not become lax in the event that
you do get some "offensive" Bunkers established. You've just put the
other player under siege, so naturally, he's going to try to make air units
and/or transports to strike directly at your undefended town. Don't get
lulled into complacency! Another tactic your enemy might try is making
long range units like Tanks or Reavers to break the siege. Using a
ComSat sweep to check the enemy town can alert you to what your
enemy is trying, so you can plan a pre-emptive strike. Be sure to take the
opportunity to make an expansion towns while your opponent is pinned
down.

Building your town
The most conservative early game strategy would be to build up your town
defensively and prepare for a rush, which is to be expected of Zerg and
Protoss players. Don't build your town haphazardly. Use Supply Depots
and your Barrack(s) as walls to seal off a whole side of your town. You'll
definitely want to build two Bunkers at the outset. Be sure the Bunkers
fulfill the following criteria, listed in order of importance:
1. At least one is within firing range of your harvesting line
2. Both are within firing range of each other
3. At least one is protecting your Barrack(s)
4. Bunkers have one side or more sides flush against others
building, to prevent large numbers of enemies from surrounding it.
5. Bunkers are protecting as many Supply Depots as possible.

Of course, it will be quite difficult, depending on how the map is laid out,
to fulfill each of the five suggestions. Sometimes you may not even want
to fulfill criteria 1, if there is a natural chokepoint to your base. You'll want
to seal off that chokepoint with your Barracks, Supply Depot and Bunkers
in the hopes that you can prevent your opponent from coming near your
workers in the first place.

The art of building a good town comes with practice. The main thing is
that your Bunkers need to protect your SCVs and be within firing range of
one another. When the attack comes, pull off 2 or 3 SCVs from the
mineral line and repair the Bunkers as they're being attacked. This will
prolong the life of your Bunkers and frustrate the enemy. They may try to
attack the SCVs that are repairing, so have those SCVs run off and draw
the enemy troops off your Bunkers. If any of your SCVs happen to be
outside the firing range of your Bunkers, have them come closer in for
protection during the duration of the attack.

A conservative build order
1. 4 SCVs, first 3 on minerals
2. Use the fourth to make a Barracks
3. Another SCV
4. When that SCV pops out, make a Supply Depot
5. Another SCV, put it on minerals
6. The two building SCVs should finish around the same time.
Immediately start on a Marine and another SCV. Have one of your
building SCVs move to minerals and the other make a Bunker.
7. Keep alternating SCV, Marine until your meter reads "14/18," or
"15/18" then make another Supply Depot. Have your first 2 Marines
go scouting around for the enemy base.

From here on your choices will vary depending on what your scout
Marines see at the enemy base. If your opponent is making less defenses
and concentrating on developing technology (Mutalisk rush, etc.), then
making a second Barracks and going for a quick strike of Marines may be
wise. If you see that your opponent is building for a rush, go ahead and
make another Bunker or two and fill them with Marines and hunker down
for the rush. You might make a second Bunker, although going for a
Refinery and a Factory instead is also a viable plan.

Go on to the next section for tips on the mid game.

Next: Mid Game Terran Overview