take navjeevan exp. everyday in morning at 9:35a.m. from chennai central, only train going to surat from chennai,if trip is on saturday then u may opt for chennai jodhpur weekly exp. around 3:15 p.m. u will get ticket also in tatkal, otherwise catch mumbai bound trains, at 6a.m. mumbai exp, 11.30 a.m. mumbai exp, 11:15p.m. mumbai mail and from there u will get plenty of trains for surat.