I've always found it annoying that SAP does not provide any functionnality to check transport request dependencies before importing them to a target system (even limited to the obvious ones). And at least we would expect the possibility to record those dependencies manually. Which unfortunately you cannot do unless you are working with "transport control using projects", and trying to set dependencies between requests belonging to different projects...
See online help for more information in this area: http://help.sap.com/erp2005_ehp_04/helpdata/en/ce/ed31375fc9342ae10000009b38f839/content.htm
Would be great to know why SAP decided to limit this very cool feature so much. I mean: if it is a best practice to re-use abap objects, then it shoudn't be that unusual to develop a program which uses data elements created for another program whithin the same project (and you cannot put both programs into the same transport request for whatever reason...).
So if you ever faced a situation where you developped something new (which you included in transport request ZZ) and knew at the time of coding that transport request XX should be transported beforehand because you were re-using some of its components, but couldn't save this dependency anywhere which resulted in error status 8 when transport request ZZ was imported to QA system (because your colleague forgot to transport XX before going on holidays), you migth be interested in the following trick...
Open the transport organizer (tcode SE03) and click the "Display/Change request attributes" button under the "Administration" folder:
Create a new attribute that you will use to record the ID of any transport request (XX in the above example) that needs to be transported before the one selected (ZZ):
Now if you create/change a transport request (tcode SE01), the attribute that you've just created can be filled in on tab "properties" with any dependent request:
When you (or any other person) release this transport request, it is very easy to check that every request under the "ZPREV_REQUEST" attribute is already imported to your target system. And an even better option would be to automate this check in badi CTS_REQUEST_CHECK...