Smartfone GPS advice

Hey all,

Im thinking of buying my 1st smartfone and have realised that it'll be mainly for satnav (other features used less).

DO you guys have any tips or advice on what to do and what to look for?
I know things can get a little technical as ive heard the data downloads can be expensive and there are options to pre-load maps to cut down on this.
Dont know the details though.

Any and all advice is appreciated!

Thanks

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