There are some different route to get to Bromo mountains, every route has it our advantage and disadvantage, here is some 

First route from Surabaya to Bromo (via Sukapura - Cemoro Lawang)

If you’re arriving thru Surabaya, you may go directly to Bromo area without heading to Malang city. Here’s the route that you may consider as the easiest way to reach Bromo from Surabaya :

Surabaya bus station (Purabaya station) – Probolinggo city : public bus (make sure to stop inside Probolinggo bus station, otherwise you’ll get scammed)
Probolinggo bus station – Cemoro Lawang village : public minibus (the last will depart by 02.30PM)
Once arriving in Cemoro Lawang village, you may find any hotel / homestay and go with 4X4WD the next day for Sunrise Tour
Some guests also doing walking tour around Bromo crater as well

Second route start from Malang – Bromo (via Pasuruan – Wonokitri)

This route are also popular for travelers who prefer to do some road trip from Malang city. Most of visitors taking the motorbike option by day time to reach Wonokitri town and head up to reach the last village before change into Jeep to get inside Bromo national park

Malang city – Purwodadi town : stop in Nongkojajar cross road
Nongkojajar town – Tosari town : a route via hills area will be needed during ride from Nongkojajar cross road to Tosari town
Tosari town – Wonokitri town : another few kilometres deom Tosari then you will stop in Wonokitri to change into 4X4WD to explore Bromo area

And the last from Malang – Bromo (via Tumpang)

Another best-view route thru Tumpang village which followed by countryside scenery of various plantations. This route would be best explored by 4X4WD directly from Malang as the road are pretty damaged and extreme on some spots.

Malang city – Gubuk Klakah village : direct 4X4WD ride from Malang city
Stop in Gubuk Klakah village for best scenery of slopy plantation hills
Gubuk Klakah village – Bromo crater : continue by your own 4X4WD ride
Various services or packages of 4X4WD ride are available from Malang city (For information & help : 

Notes

Thus, there’s still few people heading to Bromo from more direction such as Lumajang (via Ranu Pani) or from nearby villages. Attention to all motorbike rider, beware when you drive thru Wonokitri area. You might consider to drive thru Wonokitri ONLY at daytime and avoid night time drive on this route alone as some crimes accident might appeared. This route would be safe when you drive your car and in a group as well.