For Gateway Of India visit:
Come out of station by Pf.no 1 gate(dont use subway to cross road). Walk through the foot path in front of Heritage building. There you will also find the great view of Heritage Station Building. You will find taxi's there at your side. They go for Gateway. If you want sharing(20Rs per) then just look at next corner there are Vans.
By Bus: Go straight along same side you will find bus stop. Wait at the bus stop for 111 and 112 number buses.
For...
more...

Marine drive:
By walk(recommended to enjoy): Come off near pf 1 gate, cross the road by subway in front. Walk straight along the main road from front of CST building(towards left after getting off subway). Walk till big square with garden and fountain called Hutatama Chowk. You will find BSNL building to right side. Go straight by that main road beside BSNL building. Straight till end. End will be Marine Drive. By the road you will find Churchgate station & Brabourne Stadium. You will also see Oval ground with High Court Building. Everything is there it self.

There is IRCTC's Railway Refreshment Center near Pf.no 12 which provides good and ok food. Instead it is good to go outside station. You will find delicious and cheaper cost food after getting out of Central Main gate(near pf.7) and going in left direction. South Indian and all other breakfast items with juices are there. If you got out of Old Main Gate(near Pf.1 & Subway), cross the road by subway and you will find various food stalls after coming off subway. They serve good quality food and drinks. Moreover, by the same side by walking to the left along main road in front of CST building there is Mc'Donalds. There you will find Cafe Coffee Day too. Beside Mc'Donald that small road has Pizza Hut and Subway just few steps ahead. One more good restaurant is Cannon Pav Bhaji in front of BMC building which will be exactly in front...
more...

after getting off subway. So overall you will find many food varieties near Mumbai CST station. Enjoy!

If you have around 6-8 hours before,try the following places to make your day worth.
Tourist attractions near CST.
1.Gate-way of India-15 minute ride from CST.Easy cab and bus availability just outside the station.
2.Jehangir art gallery-10 minute ride from CST.
3.Haji...
more...

Ali dargah(Mosque)-Around 7 km from CST.Bus inquiry can be done from the bus info counter out side CST.(Closed during high tides).
4.Marine Drive(Queens necklace)-Fort ferry 1 and 2 out side CST will take you here.(Visit in the evening)
5.Old women's Boot(Mhataricha Boot)-Around 10km from CST.
6.CST building-CST is itself a good heritage spot.Newly opened museum with entry fee of RS.200 and 100 for students with ID-card.
Cinema Halls near CST.
1.New Excelsior-10 minute walk from CST.
2.Sterling Multiplex-Opposite new excelsior
3.Regal(One of the oldest movie theater in India)-15 minute drive from CST and 5 minute walk from Gate way of India.
4.Metro Cinema-15 minute drive from CST.
5.Eros-10 minutes from CST.Fort ferry 2 from CST.Just outside CHURCHGATE railway station which is the Western Railway headquarter..
TIP-Try using govt.buses(BEST) and avoid cabs as they will cost you more.
PICS TAKEN FROM THE NET and are in sequence.