Available Merge Fields

Client Related
ID{$client_id}
Full Name{$client_name}
First Name{$client_first_name}
Last Name{$client_last_name}
Company Name{$client_company_name}
Email Address{$client_email}
Address 1{$client_address1}
Address 2{$client_address2}
City{$client_city}
State{$client_state}
Postcode{$client_postcode}
Country{$client_country}
Phone Number{$client_phonenumber}
Password{$client_password}
Signup Date {$client_signup_date}
Credit Balance{$client_credit}
CC Type{$client_cc_type}
CC Last 4 Digits{$client_cc_number}
CC Expiry Date{$client_cc_expiry}
Language {$client_language}
Custom Fields (Array){$client_custom_fields.1}
Status{$client_status}

Other
Company Name{$company_name}
WHMCS URL{$whmcs_url}
WHMCS Link{$whmcs_link}
Signature{$signature}

Conditional Display

You can use conditionals to display text based on other values - for example:

{if $client_company_name eq "WHMCS"}
You are from WHMCS!
{else}
You are not from WHMCS!
{/if}

{if $client_name}
Hello {$client_name}
{/if}

Looping through data

{foreach from=$array_data item=data}
{$data.option}: {$data.value}
{/foreach}