No. 1 -  These guys like bright indirect light, so place in a well-lit space.

No. 2 -  Don't over-water!  These plants store most of the water they need in their hardy leaves.  Once a month should do it.  Also, make sure to water the soil, not the  tops of plants as they'll get soggy on you.

No. 3 - Growth and change is natural.  If a leaf looks like its run its course, don't be afraid to gently remove it.  It just means there's new growth coming!

No. 4 - Fertilizing your terrarium now and then will help lengthen its life span.  You can find succulent fertilizer at your local hardware store or garden center.