pronunciation, assimilation HELP!

Could someone explain the assimilation in English?

"had to" sounds [hęd tu] or [hęt tu] or [hętu] ?
"red table" sounds [red teibl] or [ret teibl] or [reb teibl] or...

What about voiced consonants (b,v,g...) before voiceless (p,f,k..)?

In British English, the 'd' often becomes a glottal sound in connected speech, and 'to' has a schwa (sorry, I can't do phonetics on this computer). It's no exactly 'hatter', but it can be close to it. With 'red table', the can run into a single unit, with a slightly langer consonant sound in the middle, one that slurs into a 't', but does start as a 'd'.

Thank you very much!!!

Is it the same with "b-p" (bob peter), "v-f" (have five), "g-k" (dog Katie) etc.?

And what about "v-t" (have to) etc. (voiced+voiceless, but different place of articulation)?

How does it work with "voiceless+voiced" (p-b "pop band", f-v, k-g...)?

Can I get all the rules? (On the Net?)

It is the same with the ifrst, but it doesn't work for me with 'have to' because the sound isn't close enough. We assimilate when sounds are close and omit sounds when they are too much work. I'm not sure that there are complete rules, especially as things will vary from region to region. For example, glottal stops are more common in British English than American, especially in Cockney and Estuary English. If you listen to Tony Blair speaking, he often omits or reduces final 't' sounds, which is a crossover from Cockney into more mainstream british English, but I haven't heard Americans doing it. He doesn't go the whole way and drop the 't' in the middle of a word, but there is a clear influence. there are rules about omitting letters and adding letters (law and order), but I haven't seen a complete list on the subject. ;-)