1. While we (do) were doing a sight-seeing tour, our friends (lie) were lied on the beach.
2.  While Tom (play) was playing the piano, his mother (do) was doing the washing-up.
3. went/ had finished
4. was having 
5. caught
6. was watching 
7. opened/ heard/ put/ crawled
8. dropped/ was doing / didn't break 

1.While we (do).were doing...a sight-seeing tour , our friends (he....on the beach

2.While Tom (play)..was playing..the piano, his mother(do)...was doing..the washing up

3.I (go)..went.. after they (finish).had.finished..their work

4.The light went out while i (have)..was having..dinner

5.The house(catch)..caught...fire while they were sleeping

6.While Tom was reading , Amely (watch).was watching...a documentary on TV

7.The burglar (open) ..was opening..the safe when he (hear)..heard.footsteps.He inmediately (put)..put....out his torch and (crawl)..crawled..under the bed.

8.Last night i (drop)..dropped..a plate when I (do)..was doing..the washing up .Fortunately it (not/break) ..didn't break..

9.Mary and I (dance)...were dancing..the house when the telephone rang.

10.I (open) ..opened.. the letter when the wind (blow) ...was blowing.it out of my hand

11.The boyfell and hurt himself while he (ride)..was riding...a bicycle